A023590 Greatest prime divisor of 2*prime(n)+1.

5, 7, 11, 5, 23, 3, 7, 13, 47, 59, 7, 5, 83, 29, 19, 107, 17, 41, 5, 13, 7, 53, 167, 179, 13, 29, 23, 43, 73, 227, 17, 263, 11, 31, 23, 101, 7, 109, 67, 347, 359, 11, 383, 43, 79, 19, 47, 149, 13, 17, 467, 479, 23, 503, 103, 31, 11, 181, 37, 563, 7, 587, 41, 89

Offset

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Formula

a(n) = A006530(A072055(n)). - Amiram Eldar, Aug 08 2020

Mathematica

Table[FactorInteger[2Prime[n]+1][[-1, 1]], {n, 70}] (* Harvey P. Dale, Jun 22 2013 *)

Prog

(PARI) a(n) = vecmax(factor(2*prime(n)+1)[, 1]); \\ Michel Marcus, Aug 08 2020

Crossrefs

Cf. A006530, A072055.

Sequence in context: A023592 A076546 A167372 * A096919 A023594 A357099

Adjacent sequences: A023587 A023588 A023589 * A023591 A023592 A023593

Keyword

nonn

Author

Clark Kimberling

Status

approved