http://qs1969.pair.com?node_id=482057


in reply to Re^4: Algorithm for cancelling common factors between two lists of multiplicands
in thread Algorithm for cancelling common factors between two lists of multiplicands

I am not sure whether approximations are OK for your case. But if it is, have you thought about Stirling's approx and Gosper's approx for factorials?

http://mathworld.wolfram.com/StirlingsApproximation.html

-SK