A024894 Numbers k such that 5*k + 1 is prime.

2, 6, 8, 12, 14, 20, 26, 30, 36, 38, 42, 48, 50, 54, 56, 62, 66, 80, 84, 86, 92, 98, 104, 108, 114, 120, 126, 128, 132, 138, 140, 150, 152, 162, 164, 176, 182, 188, 194, 198, 204, 206, 210, 212, 218, 230, 234, 236, 240, 246, 258, 260, 264, 272, 276, 290, 294, 296, 302, 306, 314

Offset: 1

Author

Clark Kimberling

Keywords

• nonn
• easy

Comments

a(n) = (A030430(n) - 1) / 5. - Reinhard Zumkeller, Aug 15 2013

Links

• Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A030430.

Programs

Haskell

a024894 = flip div 5 . subtract 1 . a030430
-- Reinhard Zumkeller, Aug 15 2013

Magma

[n: n in [0..1000] | IsPrime(5*n+1)]; // Vincenzo Librandi, Nov 20 2010

Mathematica

Select[Range[350], PrimeQ[5 # + 1] &] (* Vincenzo Librandi, May 20 2014 *)

PARI

is(n)=isprime(5*n+1) \\ Charles R Greathouse IV, Apr 16 2012

Formula

a(n) ~ 0.8n log n. - Charles R Greathouse IV, Apr 16 2012