It's weidier than you think. It works on some runs but not others! A run where it works: (C1) ev(sum(binomial(n,k),k,1,n),simpsum); n (D1) 2 - 1 (C2) A run where it doesn't: (C1) ev(sum(k*binomial(n,k),k,1,n),simpsum); n ==== \ (D1) > k BINOMIAL(n, k) / ==== k = 1 (C2) Joshua Scholar