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A050830
Numbers k such that 157*2^k-1 is prime.
0
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
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
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