Combinations

TweedyTL · #1 $Old$ November 6th, 2009, 08:30 AM

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.

courteous · #2 $Old$ November 6th, 2009, 08:45 AM

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

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

TweedyTL · #3 $Old$ November 7th, 2009, 11:40 AM

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.

Could somebody please read my post and help me with this?