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A162237 Primes p such that p^2+3*p+1 is not prime. 1

%I

%S 11,13,17,31,41,61,71,73,79,83,89,97,101,103,107,109,127,131,149,151,

%T 167,181,191,193,197,199,211,223,227,233,241,251,269,271,277,281,283,

%U 307,311,317,331,337,347,367,383,389,397,401,409,421,431,433,439,443

%N Primes p such that p^2+3*p+1 is not prime.

%H Vincenzo Librandi, <a href="/A162237/b162237.txt">Table of n, a(n) for n = 1..1000</a>

%e p=11, p^2+3*p+1=155=5*31; p=13, p^2+3*p+1=209=11*19; p=17, p^2+3*p+1=341=11*31.

%t Select[Range[0, 500], PrimeQ[#] && !PrimeQ[#^2 + 3 # + 1] &] (* _Vincenzo Librandi_, Sep 11 2013

%o (MAGMA) [p: p in PrimesUpTo(500) | not IsPrime(p^2+3*p+1)]; // _Vincenzo Librandi_, Sep 11 2013

%Y Cf. A153590.

%K nonn,easy

%O 1,1

%A _Vincenzo Librandi_, Jun 28 2009

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Last modified August 8 12:17 EDT 2022. Contains 356009 sequences. (Running on oeis4.)