A153245 Numbers n>1 such that 6*n-7 is not prime.

7, 12, 14, 17, 21, 22, 25, 27, 28, 32, 35, 36, 37, 38, 42, 47, 49, 51, 52, 55, 56, 57, 58, 62, 63, 64, 67, 69, 70, 72, 74, 77, 80, 82, 84, 87, 89, 90, 91, 92, 93, 97, 98, 102, 103, 105, 106, 107, 112, 113, 116, 117, 119, 120, 122, 123, 124, 126, 127, 129, 131, 132, 133

Offset: 1

Author

Vincenzo Librandi, Dec 21 2008

Keywords

• nonn
• easy

Comments

One more than the associated value in A046953. - R. J. Mathar, Jan 05 2011

Examples

			Distribution of the terms in the following triangular array:
*;
*,*;
*,7,*;
*,*,*,*;
*,*,14,*,*;
*,12,*,*,25,*;
*, *,*,*,*, *,*;
*,*,21,*,*,38,*,*;
*,17,*,*,36,*,*,55,*;
*,*, *,*,*, *,*,*, *,*;
*,*,28,*,*,51,*,*,74,*,*;
*,22,*,*,47,*,*,72,*,*,97,*; etc.
where * marks the non-integer values of (2*h*k + k + h + 4)/3 with h >= k >= 1. - _Vincenzo Librandi_, Jan 17 2013
		

Links

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

Crossrefs

Cf. A046953, A153134, A153135.

Programs

Magma

[n: n in [2..150] | not IsPrime(6*n - 7)]; // Vincenzo Librandi, Jan 12 2013

Mathematica

Select[Range[2, 200], !PrimeQ[6 # - 7] &] (* Vincenzo Librandi, Jan 12 2013 *)

Extensions

More terms from Vladimir Joseph Stephan Orlovsky, Dec 23 2008