Mutation effects in ordered trees
  A mutation will affect an individual and some or all of its descendants. In this paper, we investigate ordered trees with a distinguished vertex called the mutator. We describe various mutations in ordered trees, and find the generating functions for statistics concerning trees with those mutations. The examples give new interpretations to several known sequences and also introduce many new sequences and their combinatorial interpretations. 
Gi-Sang Cheon, Hana Kim and Louis W. Shapiro
math.CO