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%I #22 Sep 08 2022 08:45:52
%S 3,6,15,18,21,24,27,33,57,60,63,66,75,78,87,90,96,108,111,117,129,138,
%T 141,144,147,153,159,165,168,171,180,186,189,201,204,222,228,231,234,
%U 237,243,246,249,252,255,258,264,273,294,309,312,315,321,339,348,351
%N Numbers n such that 2*n^2 + 6*n + 1 is prime.
%C Conjecture: If p=2*n^2+6*n+1 is prime then 2^p-1 is not prime.
%C Tested for all p < 24036583 = A000043(41). - _Joerg Arndt_, Oct 06 2012
%H Vincenzo Librandi, <a href="/A176547/b176547.txt">Table of n, a(n) for n = 1..1000</a>
%e For n=3, p=37 and 2^37-1 = 223 * 616318177.
%t Select[Range[500], PrimeQ[2 #^2 + 6 # + 1] &] (* _Vincenzo Librandi_, Oct 08 2012 *)
%o (Magma) [n: n in [1..1000]| IsPrime(2*n^2 + 6*n + 1)];
%o (PARI) is(n)=isprime(2*n^2+6*n+1) \\ _Charles R Greathouse IV_, Jun 13 2017
%K nonn,easy
%O 1,1
%A _Vincenzo Librandi_, Apr 20 2010
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