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 A099047 #15 Aug 23 2019 14:25:00
%S A099047 5,7,9,11,13,15,17,19,21,23,25,26,27,29,31,33,34,35,37,39,41,43,45,47,
%T A099047 49,50,51,53,55,56,57,59,61,63,64,65,67,69,71,73,75,76,77,79,81,83,85,
%U A099047 86,87,89,91,92,93,94,95,97,99,101,103,105,107,109,111,113,115,116,117
%N A099047 Numbers n such that n-1 and n+1 are both composite.
%H A099047 Reinhard Zumkeller, <a href="/A099047/b099047.txt">Table of n, a(n) for n = 1..10000</a>
%t A099047 Select[Range[6! ],!PrimeQ[ #-1]&&!PrimeQ[ #+1]&] (* _Vladimir Joseph Stephan Orlovsky_, Apr 26 2010 *)
%t A099047 Select[Range[120],AllTrue[#+{1,-1},CompositeQ]&] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, May 10 2018 *)
%t A099047 Mean/@SequencePosition[Table[If[CompositeQ[n],1,0],{n,120}],{1,_,1}] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Aug 23 2019 *)
%o A099047 (PARI) for(n=5,200,if(!isprime(n-1)&&!isprime(n+1),print1(n,",")))
%o A099047 (Haskell)
%o A099047 a099047 n = a099047_list !! (n-1)
%o A099047 a099047_list = [m | m <- [1..],
%o A099047 a010051' (m - 1) == 0 && a010051' (m + 1) == 0]
%o A099047 -- _Reinhard Zumkeller_, Aug 04 2015
%Y A099047 Cf. A010051, A002808, A104278.
%K A099047 nonn
%O A099047 1,1
%A A099047 _Rick L. Shepherd_, Nov 13 2004