Have a look over it. Comments/suggestions/corrections all welcome.
Hopefully lots of people will get benefit from this (if they know about it, that is!).
"The physicists defer only to mathematicians, and the mathematicians defer only to God ..." - Leon M. Lederman
A very useful tool for learning.
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.