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 A089531 #18 Sep 08 2022 08:45:12
%S A089531 7,13,17,29,37,41,61,89,97,109,137,149,181,197,229,257,277,281,317,
%T A089531 337,349,389,397,401,449,457,461,541,557,569,617,677,701,709,761,769,
%U A089531 797,821,881,929,937,977,1009,1021,1049,1097,1117,1129,1201,1217,1229,1237
%N A089531 Primes p such that (p-3)/2 is also prime.
%H A089531 Vincenzo Librandi, <a href="/A089531/b089531.txt">Table of n, a(n) for n = 1..1000</a>
%F A089531 a(n) = 2*A023204(n) + 3.
%t A089531 Clear[lst,n,f] f[n_]:=PrimeQ[(n-3)/2]; lst={};Do[p=Prime[n];If[f[p],AppendTo[lst,p]],{n,6!}];lst (* _Vladimir Joseph Stephan Orlovsky_, Oct 13 2009 *)
%t A089531 Select[Prime[Range[300]], PrimeQ[(# - 3) / 2]&] (* _Vincenzo Librandi_, Apr 13 2013 *)
%o A089531 (Magma) [p: p in PrimesUpTo(1300) | IsPrime((p-3) div 2)]; // _Vincenzo Librandi_, Apr 13 2013
%o A089531 (PARI) is(n)=isprime(n) && isprime((n-3)\2) \\ _Charles R Greathouse IV_, Sep 09 2014
%Y A089531 Cf. A023204, A089530, A089532.
%K A089531 nonn,easy
%O A089531 1,1
%A A089531 _Ray Chandler_, Nov 07 2003
%E A089531 Comment from _Juri-Stepan Gerasimov_ used as new name (old name moved to formulas). - _Charles R Greathouse IV_, Sep 09 2014