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A269544
Numbers n such that 7*8^n + 1 is prime.
2
2, 40, 58, 60, 130, 144, 752, 7462, 18162, 69028, 187272, 268178, 270410, 497284, 713304, 722600, 1005254
OFFSET
1,1
COMMENTS
a(n) is even because 7*8^(2*k+1) + 1 is divisible by 3.
FORMULA
a(n) = A032353(n)/3 where this is an integer.
MATHEMATICA
Select[Range[0, 200000, 2], PrimeQ[7*8^# + 1] &]
PROG
(PARI) is(n)=ispseudoprime(7*8^n+1) \\ Charles R Greathouse IV, Jun 13 2017
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Robert Price, Feb 29 2016
STATUS
approved