Project Euler is a series of challenging mathematical/computer programming problems. Please see the site and rules before posting.
(copied from Project Euler site)
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.
The motivation for starting Project Euler, and its continuation, is to provide a platform for the inquiring mind to delve into unfamiliar areas and learn new concepts in a fun and recreational context.
Project Euler does not want their participants asking elsewhere, they want them to experiment, solve easier sub-problems, etc.
They do not want answers, or parts of answers, publicly visible.