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 A093022 #15 Aug 17 2021 07:13:04 %S A093022 4,18,23,37,42,56,61,75,80,99,103,117,122,136,141,155,160,179,184,198, %T A093022 202,216,221,235,240,259,264,278,283,297,301,315,320,339,344,358,363, %U A093022 377,382,396,400,419,424,438,443,457,462,476,481,495,508,513,527,532 %N A093022 Indices of terms in A093019 with value 2. %C A093022 Integers which require a following 2 to have a valid Luhn mod 10 check digit. %H A093022 Reinhard Zumkeller, <a href="/A093022/b093022.txt">Table of n, a(n) for n = 1..10000</a> %H A093022 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 A093022 Webopedia, <a href="http://www.webopedia.com/TERM/L/Luhn_formula.html">Luhn formula</a> %H A093022 Wikipedia, <a href="http://en.wikipedia.org/wiki/Luhn_algorithm">Luhn algorithm</a> %H A093022 <a href="/index/De#decimal_expansion">Index entries for sequences related to decimal expansion of n</a> %F A093022 A093019(a(n)) = 2. - _Reinhard Zumkeller_, Nov 08 2014 %e A093022 18 is in the sequence because A093019(18)=2; 182 has a valid Luhn mod 10 check digit. %o A093022 (Haskell) %o A093022 a093022 n = a093022_list !! (n-1) %o A093022 a093022_list = filter ((== 2) . a093019) [0..] %o A093022 -- _Reinhard Zumkeller_, Nov 08 2014 %Y A093022 Cf. A093017-A093029. %K A093022 easy,nonn,base %O A093022 1,1 %A A093022 _Ray Chandler_, Apr 03 2004 %E A093022 Offset changed by _Reinhard Zumkeller_, Nov 08 2014