number of labellings on a tree with given degrees

Tags: #theorem

Statement

Let d1,,dn with each di1 and di=2(n1). The number of labelled trees on n vertices with the degree of the ith vertex di is equal to

(n2d11,d21,,dn1)=(n2)!(d11)!(d21)!(dn1)!

Proof

This is exactly the coefficient of x1d1xndn in Fn defined in proof 1 of Cayley's formula.

For proof 2, note that these correspond to codes (c1,,cn2) such that each i appears di1 times in the code.