I am from Germany (Saarland, Saarbrücken). My favourite
- www.primepuzzles.net by
- Al Zimmermann's Programming Contests
- Natalia Makarova's Contests (magic squares and primes)
- Poor man's Programming Contests by Marcos Donnantuoni
- Hard Puzzles Contests by Jean-Charles Meyrignac
For Prime Puzzle 846, my best solution is only 69 (best
solution is 41). I will try to improve 844 and 846.
For Puzzle 844 the best solution must be higher than 221.
For Prime Puzzle 749 Natalia Makarova was so nice to
send some of my results.