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 A172017 #11 Jan 11 2025 14:03:25
%S A172017 119,121,143,145,185,187,203,205,215,217,287,289,299,301,413,415,515,
%T A172017 517,527,529,533,535,551,553,581,583,695,697,779,781,791,793,815,817,
%U A172017 869,871,893,895,899,901,959,961,1055,1057,1079,1081,1133,1135,1139
%N A172017 Twin semiprimes: nonprimes of the form 6*k-+1 where 6*k-+1 are both semiprime.
%H A172017 Harvey P. Dale, <a href="/A172017/b172017.txt">Table of n, a(n) for n = 1..2000</a>
%t A172017 Select[{#-1,#+1}&/@(6*Range[200]),PrimeOmega[#]=={2,2}&]//Flatten (* _Harvey P. Dale_, Nov 14 2018 *)
%Y A172017 Cf. A001358 (semiprimes), A171697 (twin natural nonprimes).
%K A172017 nonn
%O A172017 1,1
%A A172017 _Juri-Stepan Gerasimov_, Jan 22 2010
%E A172017 Corrected (623,625 removed) by _R. J. Mathar_, May 22 2010