Redundant generating functions in lattice path enumeration

Jong Hyun Kim

Published 2011-07-20, updated 2012-03-13Version 2

A redundant generating function is a generating function having terms which are not part of the solution of the original problem. We use redundant generating functions to study two path problems. In the first application we explain a surprising occurrence of Catalan numbers in counting paths that stay below the line y = 2x. In the second application we prove a conjecture of Niederhausen and Sullivan.