A024897 Numbers k such that 5*k + 4 is prime.

3, 5, 11, 15, 17, 21, 27, 29, 35, 39, 45, 47, 53, 69, 71, 75, 77, 81, 83, 87, 89, 95, 99, 101, 113, 119, 123, 131, 141, 143, 147, 153, 161, 165, 167, 171, 183, 185, 201, 203, 207, 209, 213, 221, 225, 245, 249, 251, 255, 257, 263, 279, 281, 285, 287, 291, 297, 299, 309, 311, 315

Offset: 1

Author

Clark Kimberling

Keywords

• nonn
• easy

Links

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

Crossrefs

Cf. A023218 (subsequence of primes).

Programs

Magma

[n: n in [1..1000] | IsPrime(5*n+4)] // Vincenzo Librandi, Nov 20 2010

Maple

A024897:=n->`if`(isprime(5*n+4), n, NULL): seq(A024897(n), n=1..500); # Wesley Ivan Hurt, Sep 07 2016

Mathematica

Select[Range[400], PrimeQ[5 # + 4]&] (* Vincenzo Librandi, Sep 25 2012 *)

PARI

isok(n) = isprime(5*n+4) \\ Michel Marcus, Sep 07 2016