I found this useful site where you can search for equations.
Welcome to the forum.
In mathematics, you don't understand things. You just get used to them.
Of course that result can be rigorously obtained, but who cares?
Combinatorics is Algebra and Algebra is Combinatorics.
Hi lightningbolt ... nice domain name.
"The physicists defer only to mathematicians, and the mathematicians defer only to God ..." - Leon M. Lederman