A089241 Even numbers k such that k/2 - 1 is prime.

6, 8, 12, 16, 24, 28, 36, 40, 48, 60, 64, 76, 84, 88, 96, 108, 120, 124, 136, 144, 148, 160, 168, 180, 196, 204, 208, 216, 220, 228, 256, 264, 276, 280, 300, 304, 316, 328, 336, 348, 360, 364, 384, 388, 396, 400, 424, 448, 456, 460, 468, 480, 484

Offset: 1

Author

Giovanni Teofilatto, Dec 22 2003

Keywords

• easy
• nonn

References

• M. Cerasoli, F. Eugeni and M. Protasi, Elementi di Matematica Discreta, Bologna 1988
• Emanuele Munarini and Norma Zagaglia Salvi, Matematica Discreta,UTET, CittaStudiEdizioni, Milano 1997

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..5000

Crossrefs

a(n) = A072055(n) + 1.

a(n) = A029933(A000040(n)).

Programs

Magma

[2*NthPrime(n)+2: n in [1..60]]; // Vincenzo Librandi, Jan 09 2018

Mathematica

2Prime[Range[100]] + 2 (* Alonso del Arte, Mar 06 2017 *)

PARI

a(n)=2*prime(n) + 2 \\ Charles R Greathouse IV, Mar 06 2017

Formula

a(n) = 2*prime(n) + 2. - Alonso del Arte, Mar 02 2017

Extensions

Corrected (62 replaced by 64, 202 replaced by 204, 314 by 316, 386 by 388) by R. J. Mathar, Apr 22 2010

Offset corrected by Arkadiusz Wesolowski, Aug 09 2011