A023592 Least odd prime divisor of 2*prime(n)+1.

5, 7, 11, 3, 23, 3, 5, 3, 47, 59, 3, 3, 83, 3, 5, 107, 7, 3, 3, 11, 3, 3, 167, 179, 3, 7, 3, 5, 3, 227, 3, 263, 5, 3, 13, 3, 3, 3, 5, 347, 359, 3, 383, 3, 5, 3, 3, 3, 5, 3, 467, 479, 3, 503, 5, 17, 7, 3, 3, 563, 3, 587, 3, 7, 3, 5, 3, 3, 5, 3, 7, 719, 3, 3, 3, 13, 19, 3, 11, 3

Offset: 1

Author

Clark Kimberling

Keywords

• nonn

Links

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

Crossrefs

Except for first term, same as A094460.

Programs

Mathematica

Table[FactorInteger[2*Prime[n] + 1][[1, 1]], {n, 1, 80}] (* Amiram Eldar, Mar 05 2020 *)

PARI

a(n) = factor(2*prime(n)+1)[1, 1]; \\ Michel Marcus, Oct 02 2013