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

Say I have n different numbers, http://www.mathhelpforum.com/math-he...4d00b6cb-1.gif

I wish to find the summation of every possible way of multiplying http://www.mathhelpforum.com/math-he...155c67a6-1.gif different numbers together.

For clarification: if http://www.mathhelpforum.com/math-he...ec82816c-1.gif I would want:

http://www.mathhelpforum.com/math-he...e0c084ff-1.gif

If http://www.mathhelpforum.com/math-he...73fb80de-1.gif i would want:

http://www.mathhelpforum.com/math-he...472ed53c-1.gif

Basically, I just need a function http://www.mathhelpforum.com/math-he...802e72e4-1.gif that gives this result.