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%I #34 Jan 30 2021 11:42:53
%S 1,2,4,6,8,10,14,16,18,20,24,28,30,34,36,38,44,46,50,56,58,60,64,66,
%T 76,78,80,84,86,88,90,94,98,104,106,116,118,120,128,130,134,140,144,
%U 148,150,154,156,160,164,168,170,174,186,188,190,196,198,200,206,214,216
%N Numbers n such that 3n - 1 is a prime.
%C 3*n - 1 is an Eisenstein prime. - _Vincenzo Librandi_, Aug 08 2010
%C For all elements of this sequence there are no pairs (x,y) of positive integers such that a(n) = 3*x*y - x + y. - _Pedro Caceres_, Jan 28 2021
%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 Reinhard Zumkeller, <a href="/A087370/b087370.txt">Table of n, a(n) for n = 1..10000</a>
%F a(n)= A024893(n) + 1 = A088879(n) + 2.
%o (Haskell)
%o a087370 n = a087370_list !! (n-1)
%o a087370_list = filter ((== 1) . a010051' . subtract 1 . (* 3)) [0..]
%o -- _Reinhard Zumkeller_, Jul 03 2015
%Y A003627 gives primes, A091177 gives prime index.
%Y Cf. A010051, subsequence of A016789, A259645.
%K easy,nonn
%O 1,2
%A _Giovanni Teofilatto_, Oct 21 2003
%E Corrected and extended by _Ray Chandler_, Oct 22 2003
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