# Math Help - Combinations

1. ## Combinations

This is a little complicated, i'll try to explain as best i can.

Say I have n different numbers,
I wish to find the summation of every possible way of multiplying different numbers together.

For clarification: if I would want:

If i would want:

Basically, I just need a function that gives this result.

2. Choosing $x$ elements out of set of $n$ elements ( $z_1, ..., z_n$) and disregarding their order is the definition of combinations.

$F(x, z_1, ..., z_n) = \frac{n(n-1)...(n-x+1)}{x!}=\frac{n!}{(n-x)!x!}={n \choose x}$

3. Except you obviously haven't read my post at all. That's not what I'm after. I'm fairly sure I explained what I'm looking for fairly clearly.
Ok, you've shown how many different terms the function will have in terms of x and n. It isn't a formula that will calculate the value of each term and add them together.