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 A161723 #18 Apr 21 2024 11:44:30
%S A161723 23,29,41,61,71,79,89,131,149,181,211,251,331,349,401,439,449,461,659,
%T A161723 691,701,709,751,769,839,929,1031,1051,1069,1231,1301,1471,1549,1601,
%U A161723 1619,1741,1759,1889,1931,2011,2081,2161,2221,2269,2399,2441,2459,2521
%N A161723 Middle members p of prime triples (p-18,p,p+18).
%C A161723 The three primes p-18, p and p+18 are not necessarily consecutive.
%H A161723 Daniel Starodubtsev, <a href="/A161723/b161723.txt">Table of n, a(n) for n = 1..10000</a>
%F A161723 {p: p in A153418 and p-18 in A153418} - _R. J. Mathar_, Sep 22 2009
%e A161723 23 is the middle in the triple of three primes (23-18=5, 23, 23+18=41) with arithmetic progression 18.
%t A161723 q=6*3; lst={}; Do[p=Prime[n]; If[PrimeQ[p-q] && PrimeQ[p+q], AppendTo[lst,p]], {n, 5000}]; lst
%t A161723 Select[Prime[Range[7,400]],AllTrue[#+{18,-18},PrimeQ]&] (* _Harvey P. Dale_, Apr 21 2024 *)
%Y A161723 Cf. A006489, A137796.
%K A161723 nonn
%O A161723 1,1
%A A161723 _Vladimir Joseph Stephan Orlovsky_, Jun 17 2009
%E A161723 Rephrased the definition - _R. J. Mathar_, Sep 22 2009