Hello, Recently I had to find the power series to 11th order of the fifth power of a polynomial of degree 11 containing all kinds of symbols. The thing that was raised to the fifth power had 139 terms. The point of course is that in this case you do not want to have the full expansion of this power because it is way too large, takes too much time, and not necesary to find the answer. However, using the series method falls back on basic::series and this uses expand() internally. The conclusion would be that power::series is a bit to eager to use basic::series. Changing the line if (!must_expand_basis && !exponent.info(info_flags::negint)) that occurs in power::series into if (!must_expand_basis && !exponent.info(info_flags::negint) && !is_a<add>(basis)) makes this calculation finish within the second. Bye, Chris Dams