Let T be an unrooted tree. The chromatic symmetric function XT , introduced by Stanley, is a sum of monomial symmetric functions corresponding to proper colorings of T . The subtree polynomial ST , first considered under a different name by Chaudhary and Gordon, is the bivariate generating function for subtrees of T by their numbers of edges and leaves. We prove that ST = , XT , where
Jeremy L. Martin, Matthew Morin, Jennifer D. Wagne