A050549 Numbers k such that 47*2^k-1 is prime.

4, 14, 70, 78, 1374, 1824, 2158, 2654, 4494, 9598, 10068, 11524, 15128, 55408, 87324, 450470, 540494, 695384, 695724

Offset

1,1

Links

Table of n, a(n) for n=1..19.

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[47*2^# - 1] & ] (* Robert Price, Dec 22 2018 *)

Prog

(PARI) is(n)=ispseudoprime(47*2^n-1) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

Sequence in context: A005501 A065606 A049372 * A222980 A321273 A322700

Adjacent sequences: A050546 A050547 A050548 * A050550 A050551 A050552

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(17)-a (19) from the Wilfrid Keller link by Robert Price, Dec 22 2018

Status

approved