A171696 Nonnegative numbers k such that neither of 6*k +- 1 is prime.

0, 20, 24, 31, 34, 36, 41, 48, 50, 54, 57, 69, 71, 79, 86, 88, 89, 92, 97, 104, 106, 111, 116, 119, 130, 132, 134, 136, 139, 141, 145, 149, 150, 154, 160, 167, 171, 174, 176, 179, 180, 189, 190, 191, 193, 196, 201, 207, 209, 211, 212, 219, 222, 223, 224, 225

Offset: 1

Author

Juri-Stepan Gerasimov, Dec 15 2009

Keywords

• nonn

Comments

A060461 is the main sequence for this entry.

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A001477.

The same as A060461, except for the initial 0.

Programs

Maple

isA171696 := proc(n) not isprime(6*n+1) and not isprime(6*n-1) ; end proc: for n from 0 to 300 do if isA171696(n) then printf("%d,",n) ; end if; end do: # R. J. Mathar, Mar 18 2010

Mathematica

Select[Range[0, 225], !Or @@ PrimeQ[6# + {-1, 1}] &] (* Amiram Eldar, Jan 21 2020 *)

PARI

is(n)=!isprime(6*n-1) && !isprime(6*n+1) \\ Charles R Greathouse IV, Feb 17 2017

Formula

a(n+1) = A060461(n).

a(n) = n + O(n/log n). - Charles R Greathouse IV, Feb 17 2017