A125743 Primes p such that (3^p - 3^((p + 1)/2) + 1)/7 is prime.

5, 31, 53, 163, 509, 1061, 13627, 20047, 28411, 50993, 71453, 272141, 1353449

Offset

1,1

Comments

PrimePi[ a(n) ] = {3, 11, 16, 38, 97, 178,...}.

Links

Table of n, a(n) for n=1..13.

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