A024902 Numbers k such that 7*k + 4 is prime.

1, 7, 9, 15, 19, 21, 25, 27, 37, 39, 49, 55, 61, 69, 79, 81, 85, 87, 91, 97, 105, 115, 117, 129, 139, 141, 145, 147, 151, 157, 159, 169, 171, 175, 189, 205, 207, 211, 217, 225, 229, 231, 237, 247, 249, 255, 261, 267, 271, 285, 289, 295, 297, 301, 307, 319, 321, 327, 339, 349

Offset: 1

Author

Clark Kimberling

Keywords

• nonn
• easy

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A045471 (associated primes).

Programs

Magma

[n: n in [1..400] | IsPrime(7*n+4)]; // Vincenzo Librandi, Nov 20 2010

Mathematica

Select[Range[400], PrimeQ[7 # + 4] &] (* Vincenzo Librandi, Sep 26 2012 *)

PARI

is(n)=isprime(7*n+4) \\ Charles R Greathouse IV, Feb 20 2017