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

2,1

Comments

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

Links

Table of n, a(n) for n=2..52.

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

Mathematica

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

Crossrefs

Cf. A005529, A144848.

Sequence in context: A225251 A178491 A319304 * A066436 A128002 A301695

Adjacent sequences: A144858 A144859 A144860 * A144862 A144863 A144864

Keyword

nonn

Author

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

Extensions

Definition clarified by Harvey P. Dale, Nov 15 2014

Status

approved