The generating function for Stern's diatomic series http://oeis.org/A002487 satisfies A(x) = (x + 1 + 1/x) A(x^2) Is anything more known about such generating functions than the stuff in R. Stephan's 2003 paper in the bibliography? It was somewhat unsatisfying to have an infinite sum replaced by an infinite product. -- Mike Stay - metaweta@gmail.com http://www.cs.auckland.ac.nz/~mike http://reperiendi.wordpress.com