A005122 Numbers k such that 8k - 1 is prime.

1, 3, 4, 6, 9, 10, 13, 16, 19, 21, 24, 25, 28, 30, 33, 34, 39, 45, 46, 48, 54, 55, 58, 60, 61, 63, 75, 76, 79, 81, 90, 91, 93, 94, 103, 105, 108, 111, 114, 115, 121, 123, 124, 129, 130, 133, 136, 138, 144, 153, 154, 160, 163, 165, 166, 171, 175, 178, 180

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn
• easy

Comments

Corresponding primes are listed in A007522. - Altug Alkan, Dec 10 2015

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A007522.

Programs

Magma

[n: n in [1..200] | IsPrime(8*n-1)]; // Vincenzo Librandi, Dec 10 2015

Maple

A005122:=n->`if`(isprime(8*n-1), n, NULL): seq(A005122(n), n=1..300); # Wesley Ivan Hurt, Dec 11 2015

Mathematica

Select[Range[160], PrimeQ[8#-1]&] (* Harvey P. Dale, Nov 25 2011 *)

PARI

isok(n) = isprime(8*n-1); \\ Michel Marcus, Dec 10 2015