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%I #23 Sep 08 2022 08:45:50
%S 59,61,79,103,109,131,149,151,163,179,239,257,271,281,293,313,359,367,
%T 389,401,419,449,479,491,499,541,569,571,593,601,619,673,677,683,691,
%U 709,719,733,761,769,821,823,829,839,857,877,883,911,919,947,953,971,983,1009
%N Primes p such that 2*p+-3 are both nonprimes.
%C In the first 10000 primes there are 5698 terms (~57% of the primes). In the 10000 primes from prime(1,000,000,000) to prime(1,000,010,000) there are 8432 primes in this sequence or ~84%. It seems likely the density of these terms within the primes slowly approaches 100%. This indicates the density of "Prime Septets", as defined in A268593 (which rely upon primes in the complement of this sequence), declines steadily at larger n. - _Richard R. Forberg_, Feb 12 2016
%H Harvey P. Dale, <a href="/A172256/b172256.txt">Table of n, a(n) for n = 1..1000</a>
%t npQ[n_]:=Module[{c=2n},!PrimeQ[c+3]&&!PrimeQ[c-3]]; Select[Prime[ Range[ 200]],npQ] (* _Harvey P. Dale_, Jan 21 2013 *)
%t Select[Prime[Range[200]],NoneTrue[2#+{3,-3},PrimeQ]&] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Jul 25 2019 *)
%o (Magma)[p: p in PrimesUpTo(1100)| not IsPrime(2*p+3)and not IsPrime(2*p-3)] // _Vincenzo Librandi_, Dec 08 2010
%o (PARI) isok(p) = isprime(p) && !isprime(2*p+3) && !isprime(2*p-3); \\ _Michel Marcus_, Feb 12 2016
%Y Cf. A000040, A131426, A141468.
%K nonn
%O 1,1
%A _Juri-Stepan Gerasimov_, Jan 30 2010
%E Corrected and extended by _Vincenzo Librandi_, Apr 01 2010
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