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A050867
Numbers k such that 231*2^k-1 is prime.
1
1, 3, 6, 7, 21, 29, 46, 49, 54, 57, 73, 90, 118, 169, 207, 267, 287, 333, 354, 366, 370, 463, 493, 497, 507, 655, 729, 735, 757, 1054, 1377, 1770, 2098, 2886, 3225, 3611, 3625, 3657, 4849, 5706, 5749, 5771, 7110, 8395, 12150, 15658, 16182, 16693, 17363
OFFSET
1,2
MATHEMATICA
Select[Range[1000], PrimeQ[231*2^# - 1] & ] (* Robert Price, Dec 29 2018 *)
PROG
(PARI) is(n)=ispseudoprime(231*2^n-1) \\ Charles R Greathouse IV, Jun 13 2017
CROSSREFS
Sequence in context: A364007 A106357 A088101 * A019248 A284042 A288295
KEYWORD
hard,nonn
AUTHOR
N. J. A. Sloane, Dec 29 1999
EXTENSIONS
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
a(50)-a(63) from the Wilfrid Keller link by Robert Price, Dec 29 2018
STATUS
approved