This graduate-level text presents an encyclopedic account of the mathematical theory and problem-solving techniques associated with enumeration problems. Its approach blends combinatorial and algebraic ideas to offer insights into a wide variety of problems, and each section of the book focuses on a specific discrete structure, advancing from elementary (often classical) results to those at research level. Subjects include the combinatorics of the ordinary generating function and the exponential generating function, the combinatorics of sequences, and the combinatorics of paths. The text is complemented by approximately 350 exercises with full solutions. 1983 edition. Foreword by Gian-Carlo Rota. References. Index.