This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A068497 #33 Jan 14 2024 12:37:56
%S A068497 13,17,43,47,59,61,67,71,73,101,103,107,109,127,137,149,151,163,167,
%T A068497 181,193,197,223,227,241,257,263,269,277,283,311,313,317,347,349,353,
%U A068497 373,383,389,397,401,409,421,433,449,457,461,463,467,479,487,503,521
%N A068497 Primes p such that 2*p+1 and 2*p-1 are composites.
%C A068497 Subsequence of A053176. - _Michel Marcus_, Jan 12 2015
%C A068497 The sequence is infinite. Among others it contains all the primes of the form 15m+/-2. - _Emmanuel Vantieghem_, Sep 19 2016
%H A068497 G. C. Greubel, <a href="/A068497/b068497.txt">Table of n, a(n) for n = 1..10000</a>
%p A068497 select(p->isprime(p) and not isprime(2*p+1) and not isprime(2*p-1),[$1..530]); # _Muniru A Asiru_, Oct 16 2018
%t A068497 lst={};Do[p=Prime[n];If[ !PrimeQ[2*p-1]&&!PrimeQ[2*p+1],AppendTo[lst,p]],{n,6!}];lst (* _Vladimir Joseph Stephan Orlovsky_, May 12 2010 *)
%t A068497 Select[Prime[Range[500]], ! PrimeQ[2*# - 1] && ! PrimeQ[2*# + 1] &] (* _G. C. Greubel_, Oct 15 2018 *)
%o A068497 (PARI) listp(nn) = {forprime(p=2, nn, if (!isprime(2*p-1) && !isprime(2*p+1), print1(p, ", ")););} \\ _Michel Marcus_, Jan 12 2015
%o A068497 (Magma) [p: p in PrimesUpTo(600) | not IsPrime(2*p+1) and not IsPrime(2*p-1)]; // _Vincenzo Librandi_, Jan 20 2015
%o A068497 (GAP) Filtered([1..530],p->IsPrime(p) and not IsPrime(2*p+1) and not IsPrime(2*p-1)); # _Muniru A Asiru_, Oct 16 2018
%K A068497 easy,nonn
%O A068497 1,1
%A A068497 _Benoit Cloitre_, Mar 25 2002