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
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