Any editorial for Inverse factorial...?

i have been trying to solve the problem of calculating nCr (combination problem) for large values of n. i encountered with a term Inverse factorial as mentioned in this editorial, but it is not at all clear for me… :frowning:
http://discuss.codechef.com/questions/3869/best-known-algos-for-calculating-ncr-m

plzz help…!!

link to calculate reverse factorial.