What does this summation do?

I was given this summation today and asked to find out what it did. So far my friend and I have run into a brick wall at every turn.

Here's the summation:

This is the only information we were given, and we interpreted and as being integers in some set of N integers, where the first integer in the set is

The problem we've run into is that when i gets to be N, j = N+1 and is therefore undefined. So we've been interpreting it as i goes from 1 to N-1. Does anyone recognize this as a famous series of some sort, or know what it does?

Thanks for any information anyone can provide,

-Ben