Here are some other places to look more math-related material. If you have any other books or articles, list them here!
+ The Book of Numbers is a fascinating book that anyone can enjoy. The author, John Conway, is one of the few mathematicians who can write about math - and make it fun and inviting. This book doesn't deal with most of the topics we cover, but I would still highly recommend this book for anyone taking 453.
+ Concrete Mathematics is a book by Ronald Graham, Donald Knuth, and Oren Patashnik. This books provides many thorough explanations of the mathematics behind probability, sequences, and generating functions. I really enjoy this book.