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 A093026 #16 Aug 17 2021 07:21:04 %S A093026 2,16,21,35,40,59,64,78,83,97,101,115,120,139,144,158,163,177,182,196, %T A093026 200,219,224,238,243,257,262,276,281,295,304,318,323,337,342,356,361, %U A093026 375,380,399,403,417,422,436,441,455,460,479,484,498,506,511,525,530 %N A093026 Indices of terms in A093019 with value 6. %C A093026 Integers which require a following 6 to have a valid Luhn mod 10 check digit. %H A093026 Reinhard Zumkeller, <a href="/A093026/b093026.txt">Table of n, a(n) for n = 1..10000</a> %H A093026 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 A093026 Webopedia, <a href="http://www.webopedia.com/TERM/L/Luhn_formula.html">Luhn formula</a> %H A093026 Wikipedia, <a href="http://en.wikipedia.org/wiki/Luhn_algorithm">Luhn algorithm</a> %H A093026 <a href="/index/De#decimal_expansion">Index entries for sequences related to decimal expansion of n</a> %F A093026 A093019(a(n)) = 6. - _Reinhard Zumkeller_, Nov 08 2014 %e A093026 16 is in the sequence because A093019(16)=6; 166 has a valid Luhn mod 10 check digit. %o A093026 (Haskell) %o A093026 a093026 n = a093026_list !! (n-1) %o A093026 a093026_list = filter ((== 6) . a093019) [0..] %o A093026 -- _Reinhard Zumkeller_, Nov 08 2014 %Y A093026 Cf. A093017-A093029. %K A093026 easy,nonn,base %O A093026 1,1 %A A093026 _Ray Chandler_, Apr 03 2004 %E A093026 Offset changed by _Reinhard Zumkeller_, Nov 08 2014