A215667 22n+1 is prime.

1, 3, 4, 9, 15, 16, 18, 19, 21, 28, 30, 31, 33, 39, 40, 43, 45, 46, 51, 58, 60, 64, 66, 73, 81, 85, 91, 94, 96, 99, 103, 105, 106, 108, 109, 115, 121, 123, 124, 130, 133, 135, 138, 144, 145, 148, 150, 151, 154, 156, 159, 165, 168, 169, 175, 178, 183, 184, 186

Offset: 1

Author

Zak Seidov, Aug 20 2012

Keywords

• nonn

Comments

First terms that are not in A125874: 19, 31, 39, 43, 46, 51, 58, 73, 85, 91 (terms with prime factor > 11).

Links

• Zak Seidov, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A141849, A125874.

Programs

Mathematica

Select[Range[200],PrimeQ[22#+1]&] (* Harvey P. Dale, May 25 2025 *)

PARI

isok(n) = isprime(22*n+1); \\ Michel Marcus, Oct 19 2013

Formula

a(n) = (A141849(n) - 1)/22.