I'm not sure why you would want to solve it many times and committing those solutions to memory? I think you would be better off using some of the time to just read some text books?
For some of Project Euler https://www2.math.upenn.edu/~wilf/gfology2.pdf is a good math book to consult. The techniques in there will allow you to solve some of the problems with just pen and paper (and perhaps a pocket calculator, if you are too lazy to do the arithmetic by hand, but no need for a full blown programmable computer), especially the first few problems if memory serves right. Eg where they ask you to add up the first few billion even terms of the Fibonacci numbers and similar; you can just derive a simple closed formula and evaluate that by hand.