On Thu, Dec 8, 2011 at 7:56 PM, Marc LeBrun <mlb at well.com> wrote: > Forgive me if I haven't read these messages carefully, or I'm restating the > obvious, but isn't this well-understood "generatingfunctionology"? > Herb Wilf's _generatingfunctionology_ is an excellent source for this and many related powerful techniques, yes. William Keith