I recommend two exciting math references.
by Herbert Wilf
Concrete Mathematics: A Foundation for Computer Science (2nd Edition)
by Ronald L. Graham, Donald E. Knuth, Oren Patashnik
Available as a hardcover book
Today, I watched the 2019 PyCon 3-hour workshop about lambda calculus and recalled reading Herbert Wilf’s beautiful presentation. Not unlike Beazley, Wilf takes the reader down a splendid rabbit hole.
Chapter 7 of the Concrete Mathematics book also exposes generating functions – if nothing else, read through the sections about domino tilings – and enjoy Knuth’s typesetting.