A book on recurrence sequences, an advanced topic in number theory, can be downloaded from this site. It deals mainly with linear recurrence sequences, and provides extensive theory, methods, and equations. While the material is quite complex, it has applications for various disciplines. The authors state, "these sequences appear almost everywhere in mathematics and computer science." The book is in draft form, and will be featured in the Surveys and Monographs series of the American Mathematical Society sometime in 2003. Until then, however, the book can be accessed here for the purpose of correcting any errors.