“Project Euler is a series of challenging mathematical/computer programming problems that will require more than just mathematical insights to solve. Although mathematics will help you arrive at elegant and efficient methods, the use of a computer and programming skills will be required to solve most problems.”
I heard about it some time ago but I looked at it just two days ago. It’s fun! :) If you learn (know) Python and you like to solve mathematical problems with your computer then try Project Euler.
Maybe I will start posting here my solutions.