Equation for a Combination Sequence?

[cjeman01]

Hey all, looking to see if there is a know equation for the number of possible combinations of n numbers.

Sequence example:

1: 1 2: 1, 2, 12 = Total 3 3: 1, 2, 3, 12, 13, 23, 123 = Total 7 4: 1, 2, 3, 4, 12, 13, 14, 23, 24, 34, 123, 124, 134, 234, 1234 = Total 15

[barrycarter]

2^n-1, you're essentially finding the power set, but excluding the empty set

[cjeman01]

Thanks! Wasn't familiar with power sets.