A153043 Numbers n > 1 such that 2*n-3 is not a prime.

2, 6, 9, 12, 14, 15, 18, 19, 21, 24, 26, 27, 29, 30, 33, 34, 36, 39, 40, 42, 44, 45, 47, 48, 49, 51, 54, 57, 59, 60, 61, 62, 63, 64, 66, 68, 69, 72, 73, 74, 75, 78, 79, 81, 82, 84, 86, 87, 89, 90, 93, 94, 95, 96, 99, 102, 103, 104, 105, 106, 108, 109, 110

Offset: 1

Author

Vincenzo Librandi, Dec 17 2008

Keywords

• nonn
• easy

Comments

One more than the associated value in A104275. - R. J. Mathar, Jan 05 2011

2*A155705(m,n)-3 = (2n+1)*(2m+1) are nonprime: all A155705(.,.) are in this sequence.

The terms after a(1) are the values of 2*h*k + k + h + 2, 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. A098090, A104275, A153040, A155705.

Programs

Magma

[n: n in [2..102] | not IsPrime(2*n-3)];  // Bruno Berselli, Mar 05 2011

Mathematica

Select[Range[2,200], !PrimeQ[2*#-3]&] (* Vladimir Joseph Stephan Orlovsky, Feb 09 2012 *)