Thanks for the "piecewise" suggestion. That works nicely. I guess it is a bug all right. Oddly, it seems specific to m(2,j). sum(min(3, j)/factorial(j), j = 1 .. infinity); returns unevaluated. Not very bright, but not wrong. sum(convert(min(3, j),piecewise)/factorial(j), j = 1 .. infinity); gives the right answer.