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%I #11 Feb 23 2017 02:46:39
%S 13,17,19,23,37,41,47,61,71,73,79,83,97,101,103,107,113,127,131,139,
%T 149,151,163,167,179,181,191,193,199,211,223,227,229,233,241,251,257,
%U 263,269,271,277,281,283,293,307,311,317,331,337,349,359,367,373,379,383,397,401
%N Primes p such that 3*p*(p-1)+1 is not prime.
%H Vincenzo Librandi, <a href="/A165681/b165681.txt">Table of n, a(n) for n = 1..1000</a>
%F A000040 \ A165682.
%F a(n) ~ n log n. - _Charles R Greathouse IV_, Feb 23 2017
%t Select[Prime[Range[90]],!PrimeQ[3#(#-1)+1]&] (* _Harvey P. Dale_, Mar 18 2011 *)
%o (PARI) is(n)=isprime(n) && !isprime(3*n*(n-1)+1) \\ _Charles R Greathouse IV_, Feb 23 2017
%Y Cf. A165682, A165683.
%K nonn,easy
%O 1,1
%A _Vincenzo Librandi_, Sep 24 2009
%E 2 and 3 removed by _R. J. Mathar_, Sep 26 2009
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