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 A093024 #15 Aug 17 2021 07:19:33 %S A093024 3,17,22,36,41,55,60,79,84,98,102,116,121,135,140,159,164,178,183,197, %T A093024 201,215,220,239,244,258,263,277,282,296,300,319,324,338,343,357,362, %U A093024 376,381,395,404,418,423,437,442,456,461,475,480,499,507,512,526,531 %N A093024 Indices of terms in A093019 with value 4. %C A093024 Integers which require a following 4 to have a valid Luhn mod 10 check digit. %H A093024 Reinhard Zumkeller, <a href="/A093024/b093024.txt">Table of n, a(n) for n = 1..10000</a> %H A093024 John Kilgo, <a href="https://web.archive.org/web/20040627030859/http://www.dotnetjohn.com/articles/articleid97.aspx">Using the Luhn Algorithm</a>, DotNetJohn.com. %H A093024 Webopedia, <a href="http://www.webopedia.com/TERM/L/Luhn_formula.html">Luhn formula</a> %H A093024 Wikipedia, <a href="http://en.wikipedia.org/wiki/Luhn_algorithm">Luhn algorithm</a> %H A093024 <a href="/index/De#decimal_expansion">Index entries for sequences related to decimal expansion of n</a> %F A093024 A093019(a(n)) = 4. - _Reinhard Zumkeller_, Nov 08 2014 %e A093024 17 is in the sequence because A093019(17)=4; 174 has a valid Luhn mod 10 check digit. %o A093024 (Haskell) %o A093024 a093024 n = a093024_list !! (n-1) %o A093024 a093024_list = filter ((== 4) . a093019) [0..] %o A093024 -- _Reinhard Zumkeller_, Nov 08 2014 %Y A093024 Cf. A093017-A093029. %K A093024 easy,nonn,base %O A093024 1,1 %A A093024 _Ray Chandler_, Apr 03 2004 %E A093024 Offset changed by _Reinhard Zumkeller_, Nov 08 2014