combinations of permutations?
I have a string of length 14 made up of 0s, 1s, and 2s. I'm trying to find the number of strings with an odd number of 2s.
So I want to sum the number of strings I can make for each odd value between 1 and 14.
I can't figure out if for each odd number of 2s, i should use or multiplied by .
I think I should use C since I am just looking for the number of possible combinations of size k, i.e. the places where the 2's will be...
(EDIT: I meant "arghh... are these combinations or permutations?)