Here's something I know there must be a way to easily figure out... but not by me! THE QUESTION... if I have x number of categories to choose from, how many combinations can I get? for example I think that if I had 4 categories there are 15 possible combinations categories A, B, C, D combinations: A B C D AB AC AD ABC ABCD BC BCD CD ACD ABD BD Am I missing any? so if 4 yeilds 15 5 yields ? 6 yields ? I'm know a pattern develops but how does it work? Sorry I've been out of school for so long and I don't know where to begin.