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

1,2

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

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 *)

Prog

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

Crossrefs

Cf. A089033, A045437, A017017.

Sequence in context: A361786 A079905 A321321 * A189669 A164028 A301729

Adjacent sequences: A154608 A154609 A154610 * A154612 A154613 A154614

Keyword

nonn,easy

Author

Vincenzo Librandi, Jan 15 2009

Extensions

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

Status

approved