You could do pretty simple problems (like the Project Euler stuff), with a few random elements to keep things interesting -- especially because the smartest people would come up with shortcuts and be able to post more frequently than those who solved it by hand.
You could do pretty simple problems (like the Project Euler stuff), with a few random elements to keep things interesting -- especially because the smartest people would come up with shortcuts and be able to post more frequently than those who solved it by hand.