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

1,1

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

Formula

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

Mathematica

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

Prog

(PARI) a(n)=2*prime(n) + 2 \\ Charles R Greathouse IV, Mar 06 2017
(Magma) [2*NthPrime(n)+2: n in [1..60]]; // Vincenzo Librandi, Jan 09 2018

Crossrefs

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

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

Sequence in context: A050992 A372011 A090259 * A280270 A368242 A315862

Adjacent sequences: A089238 A089239 A089240 * A089242 A089243 A089244

Keyword

easy,nonn

Author

Giovanni Teofilatto, Dec 22 2003

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

Status

approved