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A050559
Numbers k such that 67*2^k-1 is prime.
0
5, 9, 21, 45, 65, 77, 273, 677, 1049, 1721, 17105, 18645, 27761, 61661, 79773, 403461, 527037, 722805
OFFSET
1,1
MATHEMATICA
Select[Range[1000], PrimeQ[67*2^# - 1] & ] (* Robert Price, Dec 22 2018 *)
PROG
(PARI) is(n)=ispseudoprime(67*2^n-1) \\ Charles R Greathouse IV, Jun 13 2017
CROSSREFS
Sequence in context: A146131 A083943 A097074 * A082676 A146932 A146476
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(18) from the Wilfrid Keller link by Robert Price, Dec 22 2018
STATUS
approved