Imagine a parliament with 4 parties that can form a government (this is a parliamentary democracy, not the US style democracy). The government does not need to have a majority behind it in the parliament (in the long run it does need it but not for this example).
How many possible combinations of parties are there?
I thought you calculated this using permutations but 4/4 returns 24 and when I do this manually I only come up with 15 combinations:
ABCD ABC ABD ACD BCD AB AC AD BC BD CD A B C D
In my case order does not matter (that is, ABC and CBA is the same) and items must not repeat. Does a regular permutation calculation take this into account? If not, how do I calculate this? Something like "combination (4 elements out of of 4 elements) + combination (3 of 4) + combination (2 of 4) + combination (1 of 4)"? What is this called?