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Numbers n such that 3n^2 - 1 is prime.
2

%I #11 Jun 05 2017 10:13:48

%S 1,2,4,6,8,12,14,18,22,26,28,30,34,40,44,48,50,52,54,58,60,70,72,74,

%T 76,78,92,96,110,118,122,136,138,144,150,154,158,164,176,182,186,188,

%U 204,210,214,216,230,232,234,236,242,248,260,268,272,274,280,298,304,308

%N Numbers n such that 3n^2 - 1 is prime.

%D M. Cerasoli, F. Eugeni and M. Protasi, Elementi di Matematica Discreta, Bologna 1988

%D Emanuele Munarini and Norma Zagaglia Salvi, Matematica Discreta,UTET, CittaStudiEdizioni, Milano 1997

%H Harvey P. Dale, <a href="/A089681/b089681.txt">Table of n, a(n) for n = 1..1000</a>

%t Select[Range[500],PrimeQ[3#^2-1]&] (* _Harvey P. Dale_, Oct 09 2011 *)

%o (PARI) is(n)=isprime(3*n^2-1) \\ _Charles R Greathouse IV_, Jun 05 2017

%K easy,nonn

%O 1,2

%A _Giovanni Teofilatto_, Jan 05 2004

%E More terms from _Rick L. Shepherd_, May 18 2005