A050559 Numbers k such that 67*2^k-1 is prime.

5, 9, 21, 45, 65, 77, 273, 677, 1049, 1721, 17105, 18645, 27761, 61661, 79773, 403461, 527037, 722805

Offset

1,1

Links

Table of n, a(n) for n=1..18.

Ray Ballinger and Wilfrid Keller, List of primes k.2^n + 1 for k < 300

Wilfrid Keller, List of primes k.2^n - 1 for k < 300

Kosmaj, Riesel list k<300.

Index entries for sequences of n such that k*2^n-1 (or k*2^n+1) is prime

Mathematica

Select[Range[1000], PrimeQ[67*2^# - 1] & ] (* Robert Price, Dec 22 2018 *)

Prog

(PARI) is(n)=ispseudoprime(67*2^n-1) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

Sequence in context: A146131 A083943 A097074 * A082676 A146932 A146476

Adjacent sequences: A050556 A050557 A050558 * A050560 A050561 A050562

Keyword

hard,nonn,more

Author

N. J. A. Sloane, Dec 29 1999

Extensions

More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008

a(18) from the Wilfrid Keller link by Robert Price, Dec 22 2018

Status

approved