Puzzles sites

1.- Frank Rubin Contest Center
2.-  Macalester College POTW
3. Ed Pegg, Jr. MathPuzzle pages.
4.- Claudio Meller's "Simplemente Números"

Number patterns

1.- Patrick De Geest, World of Numbers  
2.- Magic Stars and other patterns by Harvey Heinz
3. Shyam Sunder Gupta's Number recreations

4. Mutsumi Suzuki, Magic Squares.


General references

1.- The Chris Caldwell Site
2.- Wolfram MathWorld
3. The On-Line Encyclopedia of Integer Sequences® (OEIS®), founded by Neil J. A. Sloane in 1964.
4.- Prime Curios!, by G. L. Honaker, Jr. & Chris Caldwell
5.- Mudd Math Fun Facts, by Francis Edward Su.
6. by T. D. Noe.

Codes for primes

1.- Proth.exe, by Yves Gallot. For the GFN search click here
2.- Fermat.exe for hunting small Fermat's prime factors, by Leonid Durman.
3. Mersenne primes search by GIMPS.

On Line applets

1. Factorization:
a) Jack Brennen.
b) Factoris, by XIAO Gang.
c) ECM by Dario Alpern.

2. Primality:
a) The Nth prime page
b) Germany
c) Primes by XIAO Gang.
d) Caltech

3. The number Empire (Factorization, Primality & others) by Vitalii Vanovschi.

4. Numbers Aplenty (interesting natural numbers and their properties) by Giovanni Resta.

FAQ pages

1.- This site FAQ Page
2.- Chris Caldwell's Frequently Asked Questions about Primes
3.- Ask Dr Math's FAQ Page about many mathematic issue.
4. Looking for lost web pages? Use this link.