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%I #27 Jun 07 2021 04:49:18
%S 0,1,5,8,12,21,41,42,81,105,121,377,501,2401,14597,35381,59476,120536
%N Numbers k such that 27^k + 2 is prime.
%C All terms are the exact thirds of terms of A051783 that are divisible by 3.
%H Henri & Renaud Lifchitz, <a href="http://www.primenumbers.net/prptop/searchform.php?form=3%5En%2B2&action=Search">PRP Records</a>.
%t Do[ f = 27^n + 2; If[ PrimeQ[ f ], Print[ {n, f} ] ], {n, 1, 2500} ]
%o (PARI) is(n)=ispseudoprime(27^n+2) \\ _Charles R Greathouse IV_, Feb 17 2017
%Y Cf. A051783 (3^k + 2 is prime), A087885 (5^k + 2 is prime).
%Y Cf. A090649, A109076, A113480, A138048, A138049, A138050, A087886, A113481.
%Y Cf. A176495.
%K nonn,more
%O 1,3
%A _Alexander Adamchuk_, Mar 02 2008
%E a(15)-a(17) from A051783 by _Ray Chandler_, Aug 06 2011
%E a(18) from _Robert Price_, May 12 2019
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