A Combinatorial Proof of Postnikov's Identity and a Generalized Enumeration of Labeled Trees

This is the authors' abstract. We don't add key points for this paper.

In this paper, we give a simple combinatorial explanation of a formula of A. Postnikov relating bicolored rooted trees to bicolored binary trees. We also present generalized formulas for the number of labeled k-ary trees, rooted labeled trees, and labeled plane trees.