A050830 Numbers k such that 157*2^k-1 is prime.

1, 5, 33, 97, 121, 125, 305, 445, 473, 513, 1581, 3077, 3517, 6345, 8797, 15265, 16641, 32185, 32581, 43905, 77025, 84377, 202345, 230777, 234401, 473073, 802321, 869073

Offset

1,2

Links

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

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[157*2^# - 1] & ] (* Robert Price, Dec 23 2018 *)

Prog

(PARI) is(n)=ispseudoprime(157*2^n-1) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

Sequence in context: A185212 A250225 A250273 * A211059 A292000 A146263

Adjacent sequences: A050827 A050828 A050829 * A050831 A050832 A050833

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(27)-a(28) from the Wilfrid Keller link by Robert Price, Dec 23 2018

Status

approved