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%I #9 Mar 07 2014 06:05:56
%S 11,37,47,97,167,877,2027,2293,3011,6803,8423,50221,152809,505823
%N Primes p such that (3^p + 3^((p + 1)/2) + 1)/7 is prime.
%C PrimePi[ a(n) ] = {5, 12, 15, 25, 39, 151, 307, 341, ...}.
%H Henri & Renaud Lifchitz, <a href="http://www.primenumbers.net/prptop/searchform.php?form=%283%5Ex%2B3%5Ey%2B1%29%2F7&action=Search">PRP Records</a>.
%t Do[p=Prime[n];f=(3^p+3^((p+1)/2)+1)/7;If[PrimeQ[f],Print[{n,p}]],{n,1,341}]
%Y Cf. A125743 = Primes p such that (3^p - 3^((p + 1)/2) + 1)/7 is prime. Cf. A125738 = Primes p such that 3^p - 3^((p + 1)/2) + 1 is prime. Cf. A125739 = Primes p such that 3^p + 3^((p + 1)/2) + 1 is prime. Cf. A007670, A007671, A124165, A125742.
%K hard,more,nonn
%O 1,1
%A _Alexander Adamchuk_, Dec 04 2006
%E a(9)-a(12) from Lelio R Paula (lelio(AT)sknet.com.br), May 09 2008
%E a(13)-a(14) from _Serge Batalov_, Mar 07 2014
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