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%I #25 Nov 10 2023 20:16:59
%S 3,5,11,15,51,69,99,227,381,537,9135,9737,58437,105567,121779,123645
%N Numbers k such that 3^k - 16 is prime.
%C a(17) > 2*10^5. - _Robert Price_, Sep 29 2013
%e For k = 3, 3^3 - 16 = 11 and 11 is prime. Hence k = 3 is included in the sequence.
%t Do[If[PrimeQ[3^n - 16], Print[n]], {n, 1, 10000}]
%o (PARI) is(n)=isprime(3^n-16) \\ _Charles R Greathouse IV_, Feb 17 2017
%Y Cf. Sequences of numbers k such that 3^k + m is prime:
%Y (m = 2) A051783, (m = -2) A014224, (m = 4) A058958, (m = -4) A058959,
%Y (m = 8) A217136, (m = -8) A217135, (m = 10) A217137, (m = -10) A217347,
%Y (m = 14) A219035, (m = -14) A219038, (m = 16) A205647, (m = -16) this sequence, (m = 20) A219040, (m = -20) A219041.
%Y Note that if m is a multiple of 3, 3^k + m is also a multiple of 3 (for k greater than 0), and as such isn't prime.
%K nonn,more
%O 1,1
%A _Nicolas M. Perrault_, Nov 10 2012
%E a(13)-a(16) from _Robert Price_, Sep 29 2013
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