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 A125743 Primes p such that (3^p - 3^((p + 1)/2) + 1)/7 is prime. 2
 5, 31, 53, 163, 509, 1061, 13627, 20047, 28411, 50993, 71453, 272141, 1353449 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS PrimePi[ a(n) ] = {3, 11, 16, 38, 97, 178,...}. LINKS Henri & Renaud Lifchitz, PRP Records. MATHEMATICA Do[p=Prime[n]; f=(3^p-3^((p+1)/2)+1)/7; If[PrimeQ[f], Print[{n, p}]], {n, 1, 178}] CROSSREFS Cf. A125744 = 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. Sequence in context: A238674 A245523 A147033 * A332788 A333243 A078686 Adjacent sequences: A125740 A125741 A125742 * A125744 A125745 A125746 KEYWORD hard,more,nonn AUTHOR Alexander Adamchuk, Dec 04 2006 EXTENSIONS a(6)-a(11) from Lelio R Paula (lelio(AT)sknet.com.br), May 08 2008 a(12) from Serge Batalov, Mar 07 2014 a(13) from Serge Batalov, Mar 25 2014 STATUS approved

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Last modified March 30 06:16 EDT 2023. Contains 361606 sequences. (Running on oeis4.)