Generating Functions: Enumerative Combinatorics "the most useful but most RICHARD P.STANLEY difficult to understand method (for counting)' CONCRETE MATHEMATICS AHAM KNUTH PATASHN "the most powerful way to deal with sequences of numbers,as far as anybody knows,"“the most useful but most difficult to understand method (for counting)” Generating Functions: “the most powerful way to deal with sequences of numbers, as far as anybody knows