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 A256381 #13 Sep 08 2022 08:46:11
%S A256381 7,12,18,36,52,54,88,90,118,126,158,180,206,212,216,218,250,256,262,
%T A256381 292,298,302,306,324,326,332,338,358,368,374,410,414,448,450,508,514,
%U A256381 530,532,540,548,556,562,576,586,594,626,632,652,682,684,692,700,710,720
%N A256381 Numbers n such that n-3 and n+3 are semiprimes.
%C A256381 All but the first term are even.
%t A256381 Select[Range[750], PrimeOmega[# + 3] == PrimeOmega[# - 3] == 2 &] (* _Vincenzo Librandi_, Mar 28 2015 *)
%t A256381 SequencePosition[Table[If[PrimeOmega[n]==2,1,0],{n,800}],{1,_,_,_,_,_,1}][[All,1]]+3 (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, May 21 2017 *)
%o A256381 (PARI) lista(nn,m=3) = {for (n=m+1, nn, if (bigomega(n-m)==2 && bigomega(n+m)==2, print1(n, ", ")););}
%o A256381 (Magma) IsSemiprime:=func< n | &+[k[2]: k in Factorization(n)] eq 2 >; [ n: n in [4..750] | IsSemiprime(n+3) and IsSemiprime(n-3) ]; // _Vincenzo Librandi_, Mar 28 2015
%Y A256381 Cf. A001358 (semiprimes).
%Y A256381 Cf. A124936 (n-1 and n+1), A105571 (n-2 and n+2).
%Y A256381 Cf. A256382 (n-4 and n+4), A256383 (n-5 and n+5).
%K A256381 nonn
%O A256381 1,1
%A A256381 _Michel Marcus_, Mar 27 2015