>> If N is an integer, then neither N^2-N+1 nor N^2+N+1 is divisible by >> any positive number of the form 6k+5. > I think that the proof is not comprete for A056650. > The following theorem should be proved. > T.3^n p^2+p+1=3^n , p is prime, has no solution. Well, n^2-n+1 and n^2+n+1 are never divisible by 9. That should do it. -- Don Reble djr at nk.ca