A153047 Numbers n such that 2*n-15 is not a prime.

12, 15, 18, 20, 21, 24, 25, 27, 30, 32, 33, 35, 36, 39, 40, 42, 45, 46, 48, 50, 51, 53, 54, 55, 57, 60, 63, 65, 66, 67, 68, 69, 70, 72, 74, 75, 78, 79, 80, 81, 84, 85, 87, 88, 90, 92, 93, 95, 96, 99, 100, 101, 102, 105, 108, 109, 110, 111, 112, 114, 115, 116

Offset: 1

Author

Vincenzo Librandi, Dec 17 2008

Keywords

• nonn
• easy

Comments

One more than the associated entry in A153049. - R. J. Mathar, Jan 05 2011

The terms are the values of 2*h*k + k + h + 8, where h and k are positive integers.- Vincenzo Librandi, Jan 19 2013

Links

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

Crossrefs

Cf. A097480, A153043, A153045, A153049, A163657.

Programs

Magma

[n: n in [10..120] | not IsPrime(2*n - 15)]; // Vincenzo Librandi, Oct 11 2012

Mathematica

Select[Range[12,200], !PrimeQ[2*#-15]&] (* Vladimir Joseph Stephan Orlovsky, Feb 09 2012 *)