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A032418
Numbers n such that 137 * 2^n + 1 is a prime.
2
3, 27, 39, 83, 203, 395, 467, 875, 1979, 6939, 13623, 22835, 56307, 81839, 197783, 224879, 261147, 523283, 533043, 2457639
OFFSET
1,1
EXAMPLE
137 * 2^3 + 1 = 1097 is a prime so 3 is in the sequence.
137 * 2^5 + 1 = 4385 = 5 * 877, so 5 is not in the sequence.
MATHEMATICA
Select[Range[1000], PrimeQ[137 2^# + 1] &] (* Alonso del Arte, Apr 06 2020 *)
CROSSREFS
Sequence in context: A034594 A077533 A175545 * A108163 A108114 A172969
KEYWORD
nonn,hard
EXTENSIONS
3 more terms sent by Jud McCranie, Jan 15 2000 and May 03 2000
One more term from Jud McCranie, Jun 12 2004
533043 from Jud McCranie, Oct 06 2004
a(20) = 2457639 from Jeppe Stig Nielsen, Apr 04 2020
STATUS
approved