Working out all possible combinations
I worked out the rule of working out the possible combinations like this:
All combinations of 1 number = 6
All possible combinations of 2 numbers = 6*5 = 30
All possible combinations of 3 numbers = 30*4 = 120
All possible combinations of 4 numbers = 120*3 = 360
All possible combinations of 5 numbers = 360*2 = 720
All possible combinations of 6 numbers = ?
If I carry on the rule I end up with 720 * 1, which surely isn't right. Can anyone tell me how to work out the next number?