> An aside: ?I thought that nusum(1/n^2,n,1,inf) knew that the answer is > %pi^2/6, but it doesn't now. ?Perhaps my memory is wrong. nusum in general does not work well for infinite sums. simpsum knows how to do it. (%i1) sum(1/n^2,n,1,inf)$ (%i2) %, simpsum; (%o2) %pi^2/6 Andrej