A144861 Primitive prime factors of the sequence 2k^2 - 1 in the order in which they are first found.

7, 17, 31, 71, 97, 127, 23, 199, 241, 41, 337, 449, 73, 577, 647, 103, 47, 881, 967, 151, 1151, 1249, 193, 1567, 257, 113, 89, 311, 2311, 79, 2591, 2887, 3041, 457, 3361, 3527, 3697, 4049, 4231, 631, 271, 4801, 4999, 743, 5407, 137, 263, 6271, 6961, 313, 1063

Offset: 2

Author

Bernhard Helmes (pi(AT)devalco.de), Sep 23 2008

Keywords

• nonn

Comments

Every Mersenne prime number appears on this sequence. a(n) mod 8 = 1 or 7.

Links

• Bernhard Helmes, Prime sieving on the polynomial f(n)=2n^2-1.

Crossrefs

Cf. A005529, A144848.

Programs

Mathematica

Rest[DeleteDuplicates[#[[1]]&/@(Flatten[FactorInteger/@(2*Range[100]^2-1),1])]] (* Harvey P. Dale, Nov 15 2014 *)

Extensions

Definition clarified by Harvey P. Dale, Nov 15 2014