A167462 Primes p such that 2*p-5 is composite.

7, 13, 19, 31, 37, 41, 43, 61, 67, 73, 79, 83, 97, 103, 107, 109, 113, 127, 139, 151, 157, 163, 167, 173, 181, 191, 193, 199, 211, 223, 229, 239, 241, 251, 269, 271, 277, 283, 293, 307, 313, 317, 331, 337, 347, 349, 359, 367, 373, 379, 397, 409, 419, 421

Offset: 1

Author

Vincenzo Librandi, Nov 04 2009

Keywords

• nonn
• easy

Links

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

Crossrefs

Cf. A063909.

Programs

Magma

[p: p in PrimesInInterval(4,600)| not IsPrime(2*p-5)]; // Vincenzo Librandi, Sep 15 2013

Mathematica

Select[Range[4, 3000], PrimeQ[#]&& ! PrimeQ[2 # - 5] &](* Vincenzo Librandi, Sep 15 2013 *)
Select[Prime[Range[100]],CompositeQ[2#-5]&] (* Harvey P. Dale, May 16 2016 *)

Extensions

Corrected (229 inserted) by R. J. Mathar, Nov 30 2009

Corrected (3 deleted, as 2*3-5 = 1 and 1 is not composite) by Harvey P. Dale, May 16 2016