A154611 Numbers n such that 7*n+3 is not prime.

1, 3, 5, 6, 7, 9, 11, 12, 13, 15, 16, 17, 18, 19, 20, 21, 23, 24, 25, 26, 27, 29, 30, 31, 33, 35, 36, 37, 39, 41, 42, 43, 45, 46, 47, 48, 49, 51, 53, 54, 55, 56, 57, 59, 60, 61, 62, 63, 64, 65, 66, 67, 69, 70, 71, 72, 73, 75, 76, 77, 78, 79

Offset: 1

Author

Vincenzo Librandi, Jan 15 2009

Keywords

• nonn
• easy

Comments

The even terms are the integer values of (4*h*k + 2*k + 2*h - 2)/7, where h and k are positive integers. - Vincenzo Librandi, Jan 17 2013

The corresponding composite numbers are 10, 24, 38, 45, 52, 66, 80, 87, 94, 108, 115, 122, 129, ... - Michael B. Porter, Jan 17 2013

Links

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

Crossrefs

Cf. A089033, A045437, A017017.

Programs

Magma

[n: n in [0..80] | not IsPrime(7*n+3)]; // Vincenzo Librandi, Apr 05 2013

Mathematica

With[{nn=100},Sort[Join[Range[1,nn-1,2],Select[Range[0,nn,2], !PrimeQ[ 7#+3]&]]]] (* Harvey P. Dale, Aug 22 2012 *)
Select[Range[0, 100], !PrimeQ[7 # + 3]&] (* Vincenzo Librandi, Apr 05 2013 *)

Extensions

Erroneous comments deleted by N. J. A. Sloane, Jun 23 2010