A181766 Numbers k such that 3*k + 7 is not prime.

1, 3, 5, 6, 7, 9, 11, 13, 14, 15, 16, 17, 19, 21, 23, 25, 26, 27, 28, 29, 31, 33, 35, 36, 37, 38, 39, 41, 42, 43, 45, 46, 47, 49, 51, 53, 54, 55, 56, 57, 59, 60, 61, 63, 65, 66, 67, 69, 70, 71, 73, 75, 76, 77, 79, 80, 81, 82, 83, 84, 85, 86, 87, 89, 91, 93, 94, 95, 96, 97, 98

Offset

1,2

Comments

One less than the associated value in A153282, two less than A153309. - R. J. Mathar, Jan 05 2011

Links

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

Example

Distribution of the even terms in the following triangular array:
*;
*, 6;
*, *,14;
*, *,*,*;
*,16,*,*,38;
*,*,28,*,*,54;
*,*, *,*,*, *,*;
*,26,*,*,60,*,*,94;
*,*,42,*,*,80,*,*,118;
*,*,*, *,*,*, *,*, *, *;
*,36,*,*,82,*,*,128,*,*,174;
*,*,56,*,*,106,*,*,156,*,*,206; etc.
where * marks the non-integer values of (4*h*k + 2*k + 2*h - 6)/3 with h >= k >= 1. - Vincenzo Librandi, Jan 15 2013

Mathematica

Select[Range[0, 100], !PrimeQ[3 # + 7] &] (* Vincenzo Librandi, Oct 15 2012 *)

Prog

(Magma) [n: n in [0..100] | not IsPrime(3*n + 7)]; // Vincenzo Librandi, Oct 15 2012

Crossrefs

Cf. A089953 (3*n+7 is a prime).

Cf. A153282, A153309.

Sequence in context: A320472 A064802 A233570 * A047584 A229089 A277573

Adjacent sequences: A181763 A181764 A181765 * A181767 A181768 A181769

Keyword

nonn,easy

Author

Vincenzo Librandi

Status

approved