A059749 Numbers k such that 5*2^k - 7 is prime.

1, 2, 4, 6, 10, 16, 30, 32, 52, 68, 78, 84, 118, 136, 154, 406, 488, 696, 752, 880, 2754, 3922, 3976, 4888, 5866, 51084, 55744, 61000

Offset

1,2

Comments

The next terms are > 50000. - Jinyuan Wang, Feb 03 2020

Links

Table of n, a(n) for n=1..28.

Mathematica

Do[ If[ PrimeQ[ 5*2^n - 7 ], Print[n] ], {n, 3000} ]
Select[Range[6000], PrimeQ[(5*2^# - 7)] &] (* Vincenzo Librandi, Sep 30 2012 *)

Prog

(PARI) is(n)=ispseudoprime(5*2^n-7) \\ Charles R Greathouse IV, Jun 13 2017
(PFGW) ABC2 5*2^$a-7
a: from 1 to 10000 // Jinyuan Wang, Feb 03 2020

Crossrefs

Cf. A059748 (5*2^k + 7 is prime).

Sequence in context: A018161 A288599 A067880 * A334213 A164142 A048833

Adjacent sequences: A059746 A059747 A059748 * A059750 A059751 A059752

Keyword

nonn,more

Author

Robert G. Wilson v, Feb 10 2001

Extensions

a(22)-a(25) from Vincenzo Librandi, Sep 30 2012

a(26)-a(28) from Michael S. Branicky, May 20 2023

Status

approved