- Here is a good dictionary of math terms by Eric Weisstein.
- Seton Hall sponsored an online real analysis textbook; it's really good!
- MathSoft's list of Mathematical Constants.

A great textbook, must meet several criteria: good exposition (not too arcane, not too shallow), fun problems, clean typesetting. These are the my favorite Math/CS books of all time. First my absolute favorite:

- Concrete Mathematics; Graham, Knuth, Patashnik [Probably the overall best math text I've ever seen.]

And then the runners-up:

- The Art of Computer Science, vols 1-3; Knuth [Classic, perfect.]
- Combinatorics; van Lint, Wilson [Not for the weak-hearted.]
- Generatingfunctionology; Wilf [Fun approach, fun exposition.]
- Randomized Algorithms; Motwani, Raghavan [Well-written and a cool topic.]
- Analysis of Algorithms; Sedgewick, Flajolet [Important stuff, but not an introductory text.]
- A First Course in Probability; Ross [Tons of good problems, but lots of typos.]
- Abstract Algebra; Dummit, Foote [Best algebra text I've seen.]
- Introduction to the Theory of Computation; Sipser [Sipser is a great expositor, but the book has a lot of typos.]
- Modern Computer Algebra; von zur Gathen, Gerhard [Beautifully presented, fun topics]

John's Deep Math Thought for the Day: I noticed that at the 762nd decimal place of pi there occurs the sequence 999999. Wouldn't this be the logical place to round off?

John Black's WWW Page / John R. Black / (jrblack@cs.colorado.edu)