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A032500
Numbers k such that 247*2^k+1 is prime.
1
6, 14, 18, 26, 34, 42, 56, 74, 78, 94, 132, 146, 186, 284, 302, 1758, 1816, 2336, 3374, 3466, 4522, 8058, 11114, 12456, 22172, 26208, 39794, 61512, 81576, 238734, 270794, 348972, 420034, 680694, 682974, 964444, 1076024, 1124806, 1158186, 1786968, 2082202
OFFSET
1,1
MATHEMATICA
Select[Range[1000], PrimeQ[247*2^# + 1] & ] (* Robert Price, Dec 20 2018 *)
PROG
(PARI) is(n)=ispseudoprime(247*2^n+1) \\ Charles R Greathouse IV, Jun 13 2017
CROSSREFS
Sequence in context: A260114 A340634 A156858 * A053474 A072204 A037177
KEYWORD
nonn,hard
AUTHOR
EXTENSIONS
a(30)-a(40) from the Ray Ballinger and Wilfrid Keller link by Robert Price, Dec 20 2018
a(41) from Jeppe Stig Nielsen, Jan 19 2020
STATUS
approved