Combinatorics for programmers?

Question

Books

The book should be easy to read or at least average. The level for reading such a book is the school curriculum in mathematics and computer science. It should also be expanded on CS-related topics, and should also be narrated in an easy manner. It should be a kind of introductory tutorial before starting the middle combinatorics. Well, or at least set a general view, from which you can push into other deeper topics.
PS I also wanted to ask what before. mat. I must have the knowledge to read already average books on combinatorics (already expanded for sure).
PS The book is preferably from an English-speaking author, but also from a domestic one is also suitable.

Answer 1

Combinatorics from Naum Yakovlevich Vilenkin. I read it myself two years ago. The material is digested quite easily, I still remember whole chapters and many fragments from the book. The main thing is a huge number of practical tasks. There is also an Introduction to combinatorial analysis by J. Riordan (I haven't read it myself, but I often stumbled across it in search of material).