A059747 Numbers k such that 3*2^k - 7 is prime.

2, 3, 4, 5, 8, 12, 15, 17, 20, 21, 45, 48, 87, 97, 113, 120, 172, 217, 228, 276, 312, 580, 692, 1132, 1588, 1668, 2576, 2591, 3780, 4311, 4412, 6205, 11952, 19897, 19941, 20525, 22821, 44757, 62833, 110437, 124113

Offset: 1

Author

Robert G. Wilson v, Feb 10 2001

Keywords

• nonn
• more

Comments

Next term > 12000. - Vincenzo Librandi, Sep 29 2012

Crossrefs

Cf. A059746.

Programs

Mathematica

Do[ If[ PrimeQ[ 3*2^n - 7 ], Print[n] ], {n, 3000} ]
Select[Range[6500], PrimeQ[(3*2^# - 7)] &] (* Vincenzo Librandi, Sep 29 2012 *)

PARI

is(n)=ispseudoprime(3*2^n-7) \\ Charles R Greathouse IV, Jun 13 2017

Extensions

a(29)-a(32) from Vincenzo Librandi, Sep 29 2012

a(33) from Bruno Berselli, Sep 30 2012

a(34)-a(39) from Michael S. Branicky, May 01 2023

a(40)-a(41) from Michael S. Branicky, Sep 27 2024