A034782 Numbers n such that A034693(n) = 3: 3n + 1 is prime, but neither n + 1 nor 2n + 1.

24, 32, 34, 64, 76, 80, 92, 94, 104, 110, 122, 124, 132, 144, 152, 154, 182, 202, 206, 214, 220, 236, 242, 244, 246, 252, 274, 286, 294, 302, 322, 332, 340, 344, 356, 362, 364, 374, 376, 390, 412, 416, 434, 474, 482, 484, 494, 496

Offset: 1

Author

Labos Elemer

Keywords

• nonn

Links

• Michael De Vlieger, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A034693, A034694.

Programs

Mathematica

Position[#, 3] &@ Table[k = 1; While[! PrimeQ[k n + 1], k++]; k, {n, 500}] // Flatten (* Michael De Vlieger, Mar 02 2017 *)

PARI

is(n)=!isprime(n+1)&&!isprime(2*n+1)&&isprime(3*n+1) \\ M. F. Hasler, May 13 2018

Extensions

Corrected by R. J. Mathar, Jul 26 2015

Name edited by M. F. Hasler, May 13 2018