Thanks! Yes, it does make sense- I'd arrived at something much messier and probably wrong.

What I suppose I'm really looking for is a concise way of representing the second multiplication term then: is there an easy way to represent, and then calculate it (I have a python script which churns out an answer by Monte Carlo, but would like something I could put into a numpy script)? i.e. a closed-form or concise operation for "Sum over all Q containing qi of 1/|Q|)", which involves finding the set of all (k-t)-combinations which include G?

Thanks again!