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A050556
Numbers k such that 61*2^k-1 is prime.
0
3, 5, 9, 13, 17, 19, 25, 39, 63, 67, 75, 119, 147, 225, 419, 715, 895, 1025, 1103, 1179, 1345, 1829, 3855, 4159, 4493, 6039, 7799, 9073, 10543, 12883, 23807, 23957, 36163, 44047, 51975, 65573, 79393, 79949, 81987, 86349, 384287, 499175, 762417, 971585
OFFSET
1,1
COMMENTS
499175 is also a member. - Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
MATHEMATICA
Select[Range[1000], PrimeQ[61*2^# - 1] & ] (* Robert Price, Dec 22 2018 *)
PROG
(PARI) is(n)=ispseudoprime(61*2^n-1) \\ Charles R Greathouse IV, Jun 13 2017
CROSSREFS
Sequence in context: A342474 A076052 A340377 * A138008 A063954 A123509
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(42)-a(44) from the Wilfrid Keller link by Robert Price, Dec 22 2018
STATUS
approved