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 A135441 #6 Jan 24 2022 08:02:33 %S A135441 104,410,1004,1014,1040,1041,1044,1104,1410,4010,4100,4101,4104,4110, %T A135441 4410,10004,10014,10040,10041,10044,10104,10114,10140,10141,10144, %U A135441 10145,10400,10401,10404,10410,10411,10414,10440,10441,10444,10514,11004,11014,11040 %N A135441 Numbers k such that for any single digit d of k the d-th semiprime sp(k) is substring of k. %C A135441 sp(1..9)=4,6,9,10,14,15,21,22,25, with the convention that sp(0)=1. %H A135441 David Applegate, <a href="/A135441/b135441.txt">Table of n, a(n) for n = 1..300</a> %Y A135441 Cf. A134439, A134962, A135463. %K A135441 nonn,base %O A135441 1,1 %A A135441 _Zak Seidov_, Feb 17 2008 %E A135441 Corrected and extended by _David Applegate_, Feb 18 2008