How many combinations do I get for 5 Items A,B,C,D,E if I allow pairs, triples, quadrouples:
AB, AC, .. BC, BD, ..
ABC, ABD, ABE, .. BCD, ..
ABCD, ABDE, BCDE
The combination AC is the same as CA. However, there are no AA or CC combinations.
What's the formula for this with n items that can be aranged in groups the size of 2 to n?