This requires a blender addon called "Dynamic maths expression" (https://github.com/baldingwizard/Blender-Addons/wiki/Dynamic-Maths-Expression)
It allows you to provide an maths expression and have a node tree generated from it.
Simply install the addon by going to Edit > Preferences > Addons > install addon, then select the zip that you got from the maths expression repo linked above and check the box on the maths expression addon in the list or search for it using the searchbox.
Then Open the blend file from this repo and enjoy!
