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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

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 * A078686 A031908 A139862

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 December 3 14:15 EST 2016. Contains 278745 sequences.