And then after Wilf, read Flajolet and Sedgewick: <a href="http:&#x2F;&#x2F;algo.inria.fr&#x2F;flajolet&#x2F;Publications&#x2F;book.pdf" rel="nofollow">http:&#x2F;&#x2F;algo.inria.fr&#x2F;flajolet&#x2F;Publications&#x2F;book.pdf</a>