Project Euler
I came accross the website Project Euler (https://projecteuler.net) and thought it was really great.
I don't want to take away the fun for anyone else, but wanted to publish my solutions for those who have complete to discuss further!
My solutions are not always going to be the most elegant or the most efficient, however I've stuck to the "one-minute rule" with (most of) the brute force solutions.
Highly recommend the website for anybody who's got an interest in Maths puzzles and has programming abilities.
Good luck!