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%I #20 Sep 08 2022 08:46:06
%S 7,13,17,19,43,47,67,73,97,127,137,139,157,167,193,197,199,223,227,
%T 229,269,277,283,307,337,349,353,379,383,397,409,439,463,467,487,503,
%U 523,547,557,563,599,607,613,617,643,647,739,773,797,827,853,859,887,929
%N Primes p such that 2*p+1 is not prime and 2*p+3 is prime.
%C Intersection of A023204 and A053176. - _Felix Fröhlich_, Jan 14 2017
%H Vincenzo Librandi, <a href="/A230039/b230039.txt">Table of n, a(n) for n = 1..1000</a>
%e 43 is in the sequence because 2*43+1=87 (not prime) and 2*43+3=89 (prime).
%t Select[Range[10^5],PrimeQ[#]&& !PrimeQ[2#+1]&& PrimeQ[2#+3]&]
%o (Magma) [p: p in PrimesUpTo(2500)|not IsPrime(2*p+1) and IsPrime(2*p+3)];
%o (PARI) is(n) = ispseudoprime(n) && !ispseudoprime(2*n+1) && ispseudoprime(2*n+3) \\ _Felix Fröhlich_, Jan 14 2017
%Y Cf. A005384, A023204, A053176, A126107, A163769, A230117.
%K nonn,easy
%O 1,1
%A _Vincenzo Librandi_, Oct 10 2013
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