unless you're in college, you can't enter it, but i thought that some of the problems might appeal to some of omnimaga's computer programmers. they're part of an international collegiate programming contest, so they are anything but easy. you can find links to the "problem sets" here. i found a relatively easy problem here, as problem D, bipartite numbers.

I was an ACM member, in my last few years of college. Nice thing to be a part of for sure.