Leroy Quet wrote: > Let sigma(k) = sum{j|k} j. > Let phi(k) be the number of positive integers <= k and coprime to k. > > Then for which n's is > > product{k=1 to n} sigma(k)/phi(k) > > an integer? I've got 1 2 3 4 6 7 8 14 15 and no other n up to 10000. Max