A155723 Numbers k such that 2*k + 9 is not prime.

0, 3, 6, 8, 9, 12, 13, 15, 18, 20, 21, 23, 24, 27, 28, 30, 33, 34, 36, 38, 39, 41, 42, 43, 45, 48, 51, 53, 54, 55, 56, 57, 58, 60, 62, 63, 66, 67, 68, 69, 72, 73, 75, 76, 78, 80, 81, 83, 84, 87, 88, 89, 90, 93, 96, 97, 98, 99, 100, 102, 103, 104, 105, 106, 108, 111, 113, 114

Offset

1,2

Comments

2*A155724(m,n) + 9 = (2n+1)*(2m+1) are not prime and create entries of this form. Also, one less than the associate entry in A153053, two less than the associated A153052. - R. J. Mathar, Jan 05 2011

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..10000

Example

Distribution of the terms in the following triangular array:
   0;
   3,  8;
   6, 13, 20;
   9, 18, 27,  36;
  12, 23, 34,  45,  56;
  15, 28, 41,  54,  67,  80;
  18, 33, 48,  63,  78,  93, 108;
  21, 38, 55,  72,  89, 106, 123, 140;
  24, 43, 62,  81, 100, 119, 138, 157, 176;
  27, 48, 69,  90, 111, 132, 153, 174, 195, 216;
  30, 53, 76,  99, 122, 145, 168, 191, 214, 237, 260;
  33, 58, 83, 108, 133, 158, 183, 208, 233, 258, 283, 308;
  36, 63, 90, 117, 144, 171, 198, 225, 252, 279, 306, 333, 360;
  etc.
the values of (2*h*k + k + h - 4) with h >= k >= 1. - Vincenzo Librandi, Jan 16 2013

Mathematica

Select[Range[0, 80], !PrimeQ[2*#+9]&] (* Vincenzo Librandi, Mar 01 2012 *)

Prog

(Magma) [n: n in [0..115]| not IsPrime(2*n+9)]; // Vincenzo Librandi, Mar 01 2012

Crossrefs

Cf. A155724, A155722.

Sequence in context: A153769 A275608 A363758 * A095277 A185717 A189637

Adjacent sequences: A155720 A155721 A155722 * A155724 A155725 A155726

Keyword

nonn,easy

Author

Vincenzo Librandi, Jan 25 2009

Status

approved