hacktoberfest-projecteuler

This repo contains solutions for projecteuler problems. Specially created for newcomers to contribute as part of Hacktoberfest Challenge.

List of Problems

Problem #1 Multiples of 3 and 5 || solutions
Problem #2 Even Fibonacci numbers || solutions
Problem #3 Largest prime factor || solutions
Problem #4 Largest palindrome product || solutions
Problem #5 Smallest multiple || solutions
Problem #6 Sum square difference || solutions
Problem #7 10001st prime || solutions
Problem #8 Largest product in a series || solutions
Problem #9 Special Pythagorean triplet || solutions
Problem #10 Summation of primes || solutions
Problem #11 Largest product in a grid || solutions
Problem #12 Highly divisible triangular number || solutions
Problem #13 Large sum || solutions
Problem #14 Longest Collatz sequence || solutions
Problem #15 Lattice paths || solutions
Problem #16 Power digit sum || solutions
Problem #17 Number letter counts || solutions
Problem #18 Maximum path sum I || solutions
Problem #19 Counting Sundays || solutions
Problem #20 Factorial digit sum || solutions
Problem #21 Amicable numbers || solutions
Problem #22 Names scores || solutions
Problem #23 Non-abundant sums || solutions
Problem #24 Lexicographic permutations || solutions
Problem #25 1000-digit Fibonacci number || solutions
Problem #26 Reciprocal cycles || solutions
Problem #27 Quadratic primes || solutions
Problem #28 Number spiral diagonals || solutions
Problem #29 Distinct powers || solutions
Problem #30 Digit fifth powers || solutions
Problem #31 Coin sums || solutions
Problem #32 Pandigital products || solutions
Problem #33 Digit cancelling fractions || solutions
Problem #34 Digit factorials || solutions
Problem #35 Circular primes || solutions
Problem #36 Double-base palindromes || solutions
Problem #37 Truncatable primes || solutions
Problem #38 Pandigital multiples || solutions
Problem #39 Integer right triangles || solutions
Problem #40 Champernowne's constant || solutions
Problem #41 Pandigital prime || solutions
Problem #42 Coded triangle numbers || solutions
Problem #43 Sub-string divisibility || solutions
Problem #44 Pentagon numbers || solutions
Problem #45 Triangular, pentagonal, and hexagonal || solutions
Problem #46 Goldbach's other conjecture || solutions
Problem #47 Distinct primes factors || solutions
Problem #48 Self powers || solutions
Problem #49 Prime permutations || solutions
Problem #50 Consecutive prime sum || solutions
Problem #51 Prime digit replacements || solutions
Problem #52 Permuted multiples || solutions
Problem #53 Combinatoric selections || solutions
Problem #54 Poker hands || solutions
Problem #55 Lychrel numbers || solutions
Problem #56 Powerful digit sum || solutions
Problem #57 Square root convergents || solutions
Problem #58 Spiral primes || solutions
Problem #59 XOR decryption || solutions
Problem #60 Prime pair sets || solutions
Problem #61 Cyclical figurate numbers || solutions
Problem #62 Cubic permutations || solutions
Problem #63 Powerful digit counts || solutions
Problem #64 Odd period square roots || solutions
Problem #65 Convergents of e || solutions
Problem #66 Diophantine equation || solutions
Problem #67 Maximum path sum II || solutions
Problem #68 Magic 5-gon ring || solutions
Problem #69 Totient maximum || solutions
Problem #70 Totient permutation || solutions
Problem #71 Ordered fractions || solutions
Problem #72 Counting fractions || solutions
Problem #73 Counting fractions in a range || solutions
Problem #74 Digit factorial chains || solutions
Problem #75 Singular integer right triangles || solutions
Problem #76 Counting summations || solutions
Problem #77 Prime summations || solutions
Problem #78 Coin partitions || solutions
Problem #79 Passcode derivation || solutions
Problem #80 Square root digital expansion || solutions
Problem #81 Path sum: two ways || solutions
Problem #82 Path sum: three ways || solutions
Problem #83 Path sum: four ways || solutions
Problem #84 Monopoly odds || solutions
Problem #85 Counting rectangles || solutions
Problem #86 Cuboid route || solutions
Problem #87 Prime power triples || solutions
Problem #88 Product-sum numbers || solutions
Problem #89 Roman numerals || solutions
Problem #90 Cube digit pairs || solutions
Problem #91 Right triangles with integer coordinates || solutions
Problem #92 Square digit chains || solutions
Problem #93 Arithmetic expressions || solutions
Problem #94 Almost equilateral triangles || solutions
Problem #95 Amicable chains || solutions
Problem #96 Su Doku || solutions
Problem #97 Large non-Mersenne prime || solutions
Problem #98 Anagramic squares || solutions
Problem #99 Largest exponential || solutions
Problem #100 Arranged probability || solutions
Problem #101 Optimum polynomial || solutions
Problem #102 Triangle containment || solutions
Problem #103 Special subset sums: optimum || solutions
Problem #104 Pandigital Fibonacci ends || solutions
Problem #105 Special subset sums: testing || solutions
Problem #106 Special subset sums: meta-testing || solutions
Problem #107 Minimal network || solutions
Problem #108 Diophantine reciprocals I || solutions
Problem #109 Darts || solutions
Problem #110 Diophantine reciprocals II || solutions
Problem #111 Primes with runs || solutions
Problem #112 Bouncy numbers || solutions
Problem #113 Non-bouncy numbers || solutions
Problem #114 Counting block combinations I || solutions
Problem #115 Counting block combinations II || solutions
Problem #116 Red, green or blue tiles || solutions
Problem #117 Red, green, and blue tiles || solutions
Problem #118 Pandigital prime sets || solutions
Problem #119 Digit power sum || solutions
Problem #120 Square remainders || solutions
Problem #121 Disc game prize fund || solutions
Problem #122 Efficient exponentiation || solutions
Problem #123 Prime square remainders || solutions
Problem #124 Ordered radicals || solutions
Problem #125 Palindromic sums || solutions
Problem #126 Cuboid layers || solutions
Problem #127 abc-hits || solutions
Problem #128 Hexagonal tile differences || solutions
Problem #129 Repunit divisibility || solutions
Problem #130 Composites with prime repunit property || solutions
Problem #131 Prime cube partnership || solutions
Problem #132 Large repunit factors || solutions
Problem #133 Repunit nonfactors || solutions
Problem #134 Prime pair connection || solutions
Problem #135 Same differences || solutions
Problem #136 Singleton difference || solutions
Problem #137 Fibonacci golden nuggets || solutions
Problem #138 Special isosceles triangles || solutions
Problem #139 Pythagorean tiles || solutions
Problem #140 Modified Fibonacci golden nuggets || solutions
Problem #141 Investigating progressive numbers, n, which are also square || solutions
Problem #142 Perfect Square Collection || solutions
Problem #143 Investigating the Torricelli point of a triangle || solutions
Problem #144 Investigating multiple reflections of a laser beam || solutions
Problem #145 How many reversible numbers are there below one-billion? || solutions
Problem #146 Investigating a Prime Pattern || solutions
Problem #147 Rectangles in cross-hatched grids || solutions
Problem #148 Exploring Pascal's triangle || solutions
Problem #149 Searching for a maximum-sum subsequence || solutions
Problem #150 Searching a triangular array for a sub-triangle having minimum-sum || solutions
Problem #151 Paper sheets of standard sizes: an expected-value problem || solutions
Problem #152 Writing 1/2 as a sum of inverse squares || solutions
Problem #153 Investigating Gaussian Integers || solutions
Problem #154 Exploring Pascal's pyramid || solutions
Problem #155 Counting Capacitor Circuits || solutions
Problem #156 Counting Digits || solutions
Problem #157 Solving the diophantine equation 1/a+1/b= p/10n || solutions
Problem #158 Exploring strings for which only one character comes lexicographically after its neighbour to the left || solutions
Problem #159 Digital root sums of factorisations || solutions
Problem #160 Factorial trailing digits || solutions
Problem #161 Triominoes || solutions
Problem #162 Hexadecimal numbers || solutions
Problem #163 Cross-hatched triangles || solutions
Problem #164 Numbers for which no three consecutive digits have a sum greater than a given value || solutions
Problem #165 Intersections || solutions
Problem #166 Criss Cross || solutions
Problem #167 Investigating Ulam sequences || solutions
Problem #168 Number Rotations || solutions
Problem #169 Exploring the number of different ways a number can be expressed as a sum of powers of 2 || solutions
Problem #170 Find the largest 0 to 9 pandigital that can be formed by concatenating products || solutions
Problem #171 Finding numbers for which the sum of the squares of the digits is a square || solutions
Problem #172 Investigating numbers with few repeated digits || solutions
Problem #173 Using up to one million tiles how many different "hollow" square laminae can be formed? || solutions
Problem #174 Counting the number of "hollow" square laminae that can form one, two, three, ... distinct arrangements || solutions
Problem #175 Fractions involving the number of different ways a number can be expressed as a sum of powers of 2 || solutions
Problem #176 Right-angled triangles that share a cathetus || solutions
Problem #177 Integer angled Quadrilaterals || solutions
Problem #178 Step Numbers || solutions
Problem #179 Consecutive positive divisors || solutions
Problem #180 Rational zeros of a function of three variables || solutions
Problem #181 Investigating in how many ways objects of two different colours can be grouped || solutions
Problem #182 RSA encryption || solutions
Problem #183 Maximum product of parts || solutions
Problem #184 Triangles containing the origin || solutions
Problem #185 Number Mind || solutions
Problem #186 Connectedness of a network || solutions
Problem #187 Semiprimes || solutions
Problem #188 The hyperexponentiation of a number || solutions
Problem #189 Tri-colouring a triangular grid || solutions
Problem #190 Maximising a weighted product || solutions
Problem #191 Prize Strings || solutions
Problem #192 Best Approximations || solutions
Problem #193 Squarefree Numbers || solutions
Problem #194 Coloured Configurations || solutions
Problem #195 Inscribed circles of triangles with one angle of 60 degrees || solutions
Problem #196 Prime triplets || solutions
Problem #197 Investigating the behaviour of a recursively defined sequence || solutions
Problem #198 Ambiguous Numbers || solutions
Problem #199 Iterative Circle Packing || solutions
Problem #200 Find the 200th prime-proof sqube containing the contiguous sub-string "200" || solutions
Problem #201 Subsets with a unique sum || solutions
Problem #202 Laserbeam || solutions
Problem #203 Squarefree Binomial Coefficients || solutions
Problem #204 Generalised Hamming Numbers || solutions
Problem #205 Dice Game || solutions
Problem #206 Concealed Square || solutions
Problem #207 Integer partition equations || solutions
Problem #208 Robot Walks || solutions
Problem #209 Circular Logic || solutions
Problem #210 Obtuse Angled Triangles || solutions
Problem #211 Divisor Square Sum || solutions
Problem #212 Combined Volume of Cuboids || solutions
Problem #213 Flea Circus || solutions
Problem #214 Totient Chains || solutions
Problem #215 Crack-free Walls || solutions
Problem #216 Investigating the primality of numbers of the form 2n2-1 || solutions
Problem #217 Balanced Numbers || solutions
Problem #218 Perfect right-angled triangles || solutions
Problem #219 Skew-cost coding || solutions
Problem #220 Heighway Dragon || solutions
Problem #221 Alexandrian Integers || solutions
Problem #222 Sphere Packing || solutions
Problem #223 Almost right-angled triangles I || solutions
Problem #224 Almost right-angled triangles II || solutions
Problem #225 Tribonacci non-divisors || solutions
Problem #226 A Scoop of Blancmange || solutions
Problem #227 The Chase || solutions
Problem #228 Minkowski Sums || solutions
Problem #229 Four Representations using Squares || solutions
Problem #230 Fibonacci Words || solutions
Problem #231 The prime factorisation of binomial coefficients || solutions
Problem #232 The Race || solutions
Problem #233 Lattice points on a circle || solutions
Problem #234 Semidivisible numbers || solutions
Problem #235 An Arithmetic Geometric sequence || solutions
Problem #236 Luxury Hampers || solutions
Problem #237 Tours on a 4 x n playing board || solutions
Problem #238 Infinite string tour || solutions
Problem #239 Twenty-two Foolish Primes || solutions
Problem #240 Top Dice || solutions
Problem #241 Perfection Quotients || solutions
Problem #242 Odd Triplets || solutions
Problem #243 Resilience || solutions
Problem #244 Sliders || solutions
Problem #245 Coresilience || solutions
Problem #246 Tangents to an ellipse || solutions
Problem #247 Squares under a hyperbola || solutions
Problem #248 Numbers for which Euler’s totient function equals 13! || solutions
Problem #249 Prime Subset Sums || solutions
Problem #250 250250 || solutions
Problem #251 Cardano Triplets || solutions
Problem #252 Convex Holes || solutions
Problem #253 Tidying up || solutions
Problem #254 Sums of Digit Factorials || solutions
Problem #255 Rounded Square Roots || solutions
Problem #256 Tatami-Free Rooms || solutions
Problem #257 Angular Bisectors || solutions
Problem #258 A lagged Fibonacci sequence || solutions
Problem #259 Reachable Numbers || solutions
Problem #260 Stone Game || solutions
Problem #261 Pivotal Square Sums || solutions
Problem #262 Mountain Range || solutions
Problem #263 An engineers' dream come true || solutions
Problem #264 Triangle Centres || solutions
Problem #265 Binary Circles || solutions
Problem #266 Pseudo Square Root || solutions
Problem #267 Billionaire || solutions
Problem #268 Counting numbers with at least four distinct prime factors less than 100 || solutions
Problem #269 Polynomials with at least one integer root || solutions
Problem #270 Cutting Squares || solutions
Problem #271 Modular Cubes, part 1 || solutions
Problem #272 Modular Cubes, part 2 || solutions
Problem #273 Sum of Squares || solutions
Problem #274 Divisibility Multipliers || solutions
Problem #275 Balanced Sculptures || solutions
Problem #276 Primitive Triangles || solutions
Problem #277 A Modified Collatz sequence || solutions
Problem #278 Linear Combinations of Semiprimes || solutions
Problem #279 Triangles with integral sides and an integral angle || solutions
Problem #280 Ant and seeds || solutions
Problem #281 Pizza Toppings || solutions
Problem #282 The Ackermann function || solutions
Problem #283 Integer sided triangles for which the area/perimeter ratio is integral || solutions
Problem #284 Steady Squares || solutions
Problem #285 Pythagorean odds || solutions
Problem #286 Scoring probabilities || solutions
Problem #287 Quadtree encoding (a simple compression algorithm) || solutions
Problem #288 An enormous factorial || solutions
Problem #289 Eulerian Cycles || solutions
Problem #290 Digital Signature || solutions
Problem #291 Panaitopol Primes || solutions
Problem #292 Pythagorean Polygons || solutions
Problem #293 Pseudo-Fortunate Numbers || solutions
Problem #294 Sum of digits - experience #23 || solutions
Problem #295 Lenticular holes || solutions
Problem #296 Angular Bisector and Tangent || solutions
Problem #297 Zeckendorf Representation || solutions
Problem #298 Selective Amnesia || solutions
Problem #299 Three similar triangles || solutions
Problem #300 Protein folding || solutions
Problem #301 Nim || solutions
Problem #302 Strong Achilles Numbers || solutions
Problem #303 Multiples with small digits || solutions
Problem #304 Primonacci || solutions
Problem #305 Reflexive Position || solutions
Problem #306 Paper-strip Game || solutions
Problem #307 Chip Defects || solutions
Problem #308 An amazing Prime-generating Automaton || solutions
Problem #309 Integer Ladders || solutions
Problem #310 Nim Square || solutions
Problem #311 Biclinic Integral Quadrilaterals || solutions
Problem #312 Cyclic paths on Sierpiński graphs || solutions
Problem #313 Sliding game || solutions
Problem #314 The Mouse on the Moon || solutions
Problem #315 Digital root clocks || solutions
Problem #316 Numbers in decimal expansions || solutions
Problem #317 Firecracker || solutions
Problem #318 2011 nines || solutions
Problem #319 Bounded Sequences || solutions
Problem #320 Factorials divisible by a huge integer || solutions
Problem #321 Swapping Counters || solutions
Problem #322 Binomial coefficients divisible by 10 || solutions
Problem #323 Bitwise-OR operations on random integers || solutions
Problem #324 Building a tower || solutions
Problem #325 Stone Game II || solutions
Problem #326 Modulo Summations || solutions
Problem #327 Rooms of Doom || solutions
Problem #328 Lowest-cost Search || solutions
Problem #329 Prime Frog || solutions
Problem #330 Euler's Number || solutions
Problem #331 Cross flips || solutions
Problem #332 Spherical triangles || solutions
Problem #333 Special partitions || solutions
Problem #334 Spilling the beans || solutions
Problem #335 Gathering the beans || solutions
Problem #336 Maximix Arrangements || solutions
Problem #337 Totient Stairstep Sequences || solutions
Problem #338 Cutting Rectangular Grid Paper || solutions
Problem #339 Peredur fab Efrawg || solutions
Problem #340 Crazy Function || solutions
Problem #341 Golomb's self-describing sequence || solutions
Problem #342 The totient of a square is a cube || solutions
Problem #343 Fractional Sequences || solutions
Problem #344 Silver dollar game || solutions
Problem #345 Matrix Sum || solutions
Problem #346 Strong Repunits || solutions
Problem #347 Largest integer divisible by two primes || solutions
Problem #348 Sum of a square and a cube || solutions
Problem #349 Langton's ant || solutions
Problem #350 Constraining the least greatest and the greatest least || solutions
Problem #351 Hexagonal orchards || solutions
Problem #352 Blood tests || solutions
Problem #353 Risky moon || solutions
Problem #354 Distances in a bee's honeycomb || solutions
Problem #355 Maximal coprime subset || solutions
Problem #356 Largest roots of cubic polynomials || solutions
Problem #357 Prime generating integers || solutions
Problem #358 Cyclic numbers || solutions
Problem #359 Hilbert's New Hotel || solutions
Problem #360 Scary Sphere || solutions
Problem #361 Subsequence of Thue-Morse sequence || solutions
Problem #362 Squarefree factors || solutions
Problem #363 Bézier Curves || solutions
Problem #364 Comfortable distance || solutions
Problem #365 A huge binomial coefficient || solutions
Problem #366 Stone Game III || solutions
Problem #367 Bozo sort || solutions
Problem #368 A Kempner-like series || solutions
Problem #369 Badugi || solutions
Problem #370 Geometric triangles || solutions
Problem #371 Licence plates || solutions
Problem #372 Pencils of rays || solutions
Problem #373 Circumscribed Circles || solutions
Problem #374 Maximum Integer Partition Product || solutions
Problem #375 Minimum of subsequences || solutions
Problem #376 Nontransitive sets of dice || solutions
Problem #377 Sum of digits, experience 13 || solutions
Problem #378 Triangle Triples || solutions
Problem #379 Least common multiple count || solutions
Problem #380 Amazing Mazes! || solutions
Problem #381 (prime-k) factorial || solutions
Problem #382 Generating polygons || solutions
Problem #383 Divisibility comparison between factorials || solutions
Problem #384 Rudin-Shapiro sequence || solutions
Problem #385 Ellipses inside triangles || solutions
Problem #386 Maximum length of an antichain || solutions
Problem #387 Harshad Numbers || solutions
Problem #388 Distinct Lines || solutions
Problem #389 Platonic Dice || solutions
Problem #390 Triangles with non rational sides and integral area || solutions
Problem #391 Hopping Game || solutions
Problem #392 Enmeshed unit circle || solutions
Problem #393 Migrating ants || solutions
Problem #394 Eating pie || solutions
Problem #395 Pythagorean tree || solutions
Problem #396 Weak Goodstein sequence || solutions
Problem #397 Triangle on parabola || solutions
Problem #398 Cutting rope || solutions
Problem #399 Squarefree Fibonacci Numbers || solutions
Problem #400 Fibonacci tree game || solutions
Problem #401 Sum of squares of divisors || solutions
Problem #402 Integer-valued polynomials || solutions
Problem #403 Lattice points enclosed by parabola and line || solutions
Problem #404 Crisscross Ellipses || solutions
Problem #405 A rectangular tiling || solutions
Problem #406 Guessing Game || solutions
Problem #407 Idempotents || solutions
Problem #408 Admissible paths through a grid || solutions
Problem #409 Nim Extreme || solutions
Problem #410 Circle and tangent line || solutions
Problem #411 Uphill paths || solutions
Problem #412 Gnomon numbering || solutions
Problem #413 One-child Numbers || solutions
Problem #414 Kaprekar constant || solutions
Problem #415 Titanic sets || solutions
Problem #416 A frog's trip || solutions
Problem #417 Reciprocal cycles II || solutions
Problem #418 Factorisation triples || solutions
Problem #419 Look and say sequence || solutions
Problem #420 2x2 positive integer matrix || solutions
Problem #421 Prime factors of n15+1 || solutions
Problem #422 Sequence of points on a hyperbola || solutions
Problem #423 Consecutive die throws || solutions
Problem #424 Kakuro || solutions
Problem #425 Prime connection || solutions
Problem #426 Box-ball system || solutions
Problem #427 n-sequences || solutions
Problem #428 Necklace of circles || solutions
Problem #429 Sum of squares of unitary divisors || solutions
Problem #430 Range flips || solutions
Problem #431 Square Space Silo || solutions
Problem #432 Totient sum || solutions
Problem #433 Steps in Euclid's algorithm || solutions
Problem #434 Rigid graphs || solutions
Problem #435 Polynomials of Fibonacci numbers || solutions
Problem #436 Unfair wager || solutions
Problem #437 Fibonacci primitive roots || solutions
Problem #438 Integer part of polynomial equation's solutions || solutions
Problem #439 Sum of sum of divisors || solutions
Problem #440 GCD and Tiling || solutions
Problem #441 The inverse summation of coprime couples || solutions
Problem #442 Eleven-free integers || solutions
Problem #443 GCD sequence || solutions
Problem #444 The Roundtable Lottery || solutions
Problem #445 Retractions A || solutions
Problem #446 Retractions B || solutions
Problem #447 Retractions C || solutions
Problem #448 Average least common multiple || solutions
Problem #449 Chocolate covered candy || solutions
Problem #450 Hypocycloid and Lattice points || solutions
Problem #451 Modular inverses || solutions
Problem #452 Long Products || solutions
Problem #453 Lattice Quadrilaterals || solutions
Problem #454 Diophantine reciprocals III || solutions
Problem #455 Powers With Trailing Digits || solutions
Problem #456 Triangles containing the origin II || solutions
Problem #457 A polynomial modulo the square of a prime || solutions
Problem #458 Permutations of Project || solutions
Problem #459 Flipping game || solutions
Problem #460 An ant on the move || solutions
Problem #461 Almost Pi || solutions
Problem #462 Permutation of 3-smooth numbers || solutions
Problem #463 A weird recurrence relation || solutions
Problem #464 Möbius function and intervals || solutions
Problem #465 Polar polygons || solutions
Problem #466 Distinct terms in a multiplication table || solutions
Problem #467 Superinteger || solutions
Problem #468 Smooth divisors of binomial coefficients || solutions
Problem #469 Empty chairs || solutions
Problem #470 Super Ramvok || solutions
Problem #471 Triangle inscribed in ellipse || solutions
Problem #472 Comfortable Distance II || solutions
Problem #473 Phigital number base || solutions
Problem #474 Last digits of divisors || solutions
Problem #475 Music festival || solutions
Problem #476 Circle Packing II || solutions
Problem #477 Number Sequence Game || solutions
Problem #478 Mixtures || solutions
Problem #479 Roots on the Rise || solutions
Problem #480 The Last Question || solutions
Problem #481 Chef Showdown || solutions
Problem #482 The incenter of a triangle || solutions
Problem #483 Repeated permutation || solutions
Problem #484 Arithmetic Derivative || solutions
Problem #485 Maximum number of divisors || solutions
Problem #486 Palindrome-containing strings || solutions
Problem #487 Sums of power sums || solutions
Problem #488 Unbalanced Nim || solutions
Problem #489 Common factors between two sequences || solutions
Problem #490 Jumping frog || solutions
Problem #491 Double pandigital number divisible by 11 || solutions
Problem #492 Exploding sequence || solutions
Problem #493 Under The Rainbow || solutions
Problem #494 Collatz prefix families || solutions
Problem #495 Writing n as the product of k distinct positive integers || solutions
Problem #496 Incenter and circumcenter of triangle || solutions
Problem #497 Drunken Tower of Hanoi || solutions
Problem #498 Remainder of polynomial division || solutions
Problem #499 St. Petersburg Lottery || solutions
Problem #500 Problem 500!!! || solutions
Problem #501 Eight Divisors || solutions
Problem #502 Counting Castles || solutions
Problem #503 Compromise or persist || solutions
Problem #504 Square on the Inside || solutions
Problem #505 Bidirectional Recurrence || solutions
Problem #506 Clock sequence || solutions
Problem #507 Shortest Lattice Vector || solutions
Problem #508 Integers in base i-1 || solutions
Problem #509 Divisor Nim || solutions
Problem #510 Tangent Circles || solutions
Problem #511 Sequences with nice divisibility properties || solutions
Problem #512 Sums of totients of powers || solutions
Problem #513 Integral median || solutions
Problem #514 Geoboard Shapes || solutions
Problem #515 Dissonant Numbers || solutions
Problem #516 5-smooth totients || solutions
Problem #517 A real recursion || solutions
Problem #518 Prime triples and geometric sequences || solutions
Problem #519 Tricolored Coin Fountains || solutions
Problem #520 Simbers || solutions
Problem #521 Smallest prime factor || solutions
Problem #522 Hilbert's Blackout || solutions
Problem #523 First Sort I || solutions
Problem #524 First Sort II || solutions
Problem #525 Rolling Ellipse || solutions
Problem #526 Largest prime factors of consecutive numbers || solutions
Problem #527 Randomized Binary Search || solutions
Problem #528 Constrained Sums || solutions
Problem #529 10-substrings || solutions
Problem #530 GCD of Divisors || solutions
Problem #531 Chinese leftovers || solutions
Problem #532 Nanobots on Geodesics || solutions
Problem #533 Minimum values of the Carmichael function || solutions
Problem #534 Weak Queens || solutions
Problem #535 Fractal Sequence || solutions
Problem #536 Modulo power identity || solutions
Problem #537 Counting tuples || solutions
Problem #538 Maximum quadrilaterals || solutions
Problem #539 Odd elimination || solutions
Problem #540 Counting primitive Pythagorean triples || solutions
Problem #541 Divisibility of Harmonic Number Denominators || solutions
Problem #542 Geometric Progression with Maximum Sum || solutions
Problem #543 Prime-Sum Numbers || solutions
Problem #544 Chromatic Conundrum || solutions
Problem #545 Faulhaber's Formulas || solutions
Problem #546 The Floor's Revenge || solutions
Problem #547 Distance of random points within hollow square laminae || solutions
Problem #548 Gozinta Chains || solutions
Problem #549 Divisibility of factorials || solutions
Problem #550 Divisor game || solutions
Problem #551 Sum of digits sequence || solutions
Problem #552 Chinese leftovers II || solutions
Problem #553 Power sets of power sets || solutions
Problem #554 Centaurs on a chess board || solutions
Problem #555 McCarthy 91 function || solutions
Problem #556 Squarefree Gaussian Integers || solutions
Problem #557 Cutting triangles || solutions
Problem #558 Irrational base || solutions
Problem #559 Permuted Matrices || solutions
Problem #560 Coprime Nim || solutions
Problem #561 Divisor Pairs || solutions
Problem #562 Maximal perimeter || solutions
Problem #563 Robot Welders || solutions
Problem #564 Maximal polygons || solutions
Problem #565 Divisibility of sum of divisors || solutions
Problem #566 Cake Icing Puzzle || solutions
Problem #567 Reciprocal games I || solutions
Problem #568 Reciprocal games II || solutions
Problem #569 Prime Mountain Range || solutions
Problem #570 Snowflakes || solutions
Problem #571 Super Pandigital Numbers || solutions
Problem #572 Idempotent matrices || solutions
Problem #573 Unfair race || solutions
Problem #574 Verifying Primes || solutions
Problem #575 Wandering Robots || solutions
Problem #576 Irrational jumps || solutions
Problem #577 Counting hexagons || solutions
Problem #578 Integers with decreasing prime powers || solutions
Problem #579 Lattice points in lattice cubes || solutions
Problem #580 Squarefree Hilbert numbers || solutions
Problem #581 47-smooth triangular numbers || solutions
Problem #582 Nearly isosceles 120 degree triangles || solutions
Problem #583 Heron Envelopes || solutions
Problem #584 Birthday Problem Revisited || solutions
Problem #585 Nested square roots || solutions
Problem #586 Binary Quadratic Form || solutions
Problem #587 Concave triangle || solutions
Problem #588 Quintinomial coefficients || solutions
Problem #589 Poohsticks Marathon || solutions
Problem #590 Sets with a given Least Common Multiple || solutions
Problem #591 Best Approximations by Quadratic Integers || solutions
Problem #592 Factorial trailing digits 2 || solutions
Problem #593 Fleeting Medians || solutions
Problem #594 Rhombus Tilings || solutions
Problem #595 Incremental Random Sort || solutions
Problem #596 Number of lattice points in a hyperball || solutions
Problem #597 Torpids || solutions
Problem #598 Split Divisibilities || solutions
Problem #599 Distinct Colourings of a Rubik's Cube || solutions
Problem #600 Integer sided equiangular hexagons || solutions
Problem #601 Divisibility streaks || solutions
Problem #602 Product of Head Counts || solutions

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