ABSTRACT
In this chapter, we continue the survey of enumeration methods begun in the previous one. We look at several traditional combinatorial problems, such as counting trees, computing the size of intersection of sets, and counting the number of ways of putting balls into bins. We also introduce a versatile combinatorial method, the principle of inclusion and exclusion (PIE). Beyond the usefulness of the specific results and formulas derived in the process, we view this as an opportunity to exercise our marvelous tools: the generating functions (GFs) used as enumerators.
