NJAS> I agree that A007286 and A007289 had the same definition line. I have fixed the problem. This 'problem' has a nice solution. aperm3(n) = 2*((1-I)/(1+I))^n*(1+add(binomial(n,j)*polylog(-j,I)*3^j for j in (0..n))) A007286(n) = Re(aperm3(n)) A007289(n) = Im(aperm3(n)) Peter