Obligatory mention of Wilf's "generatingfunctionology" that is also an excellent book [1]. [1] https://www.math.upenn.edu/~wilf/gfologyLinked2.pdf https://www.

Obligatory mention of Wilf's "generatingfunctionology" that is also an excellent book [1]. [1] https://www.math.upenn.edu/~wilf/gfologyLinked2.pdf https://www.math.upenn.edu/~wilf/gfologyLinked2.pdf