A062404 Numbers k such that 2*k*prime(k) + 1 is prime.

1, 2, 3, 6, 7, 11, 16, 21, 24, 27, 29, 30, 33, 40, 43, 49, 50, 51, 54, 59, 60, 68, 76, 78, 90, 93, 95, 103, 120, 125, 131, 134, 139, 156, 159, 162, 168, 178, 180, 188, 189, 196, 198, 214, 225, 231, 237, 241, 243, 246, 255, 259, 268, 273, 275, 277, 280, 285, 287, 288

Offset

1,2

Links

Harry J. Smith, Table of n, a(n) for n = 1..1000

Example

2*3*prime(3) + 1 = 2 * 3 * 5 + 1 = 31 a prime.

Maple

select(i->isprime(2*i*ithprime(i)+1), [$1..300]);  # Muniru A Asiru, Jun 29 2018

Mathematica

Select[Range[300], PrimeQ[2# Prime[#]+1]&] (* Harvey P. Dale, Sep 12 2014 *)

Prog

(PARI) select(k->isprime(2*k*prime(k)+1), [1..700])
(Magma) [n: n in [1..300] |IsPrime(2*n*NthPrime(n) + 1)]; // Vincenzo Librandi, Jun 29 2018

Crossrefs

Sequence in context: A096578 A027754 A092857 * A032875 A032842 A023773

Adjacent sequences: A062401 A062402 A062403 * A062405 A062406 A062407

Keyword

nonn

Author

Jason Earls, Jul 08 2001

Status

approved