Multiplicity(W)= N!/(n1!*n2!....ni!)

Entropy = 1/N * ln W = 1/N*ln N! - 1/N*sigma_for_all_i(ln ni!)

ln N! ~= N*ln N - N and ni/N fraction is fixed.

entropy = sigma_for_all_i(pi*ln pi) where pi = lim ni/N as N->infinity