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 A093028 #15 Aug 17 2021 06:25:55 %S A093028 1,15,20,39,44,58,63,77,82,96,100,119,124,138,143,157,162,176,181,195, %T A093028 204,218,223,237,242,256,261,275,280,299,303,317,322,336,341,355,360, %U A093028 379,384,398,402,416,421,435,440,459,464,478,483,497,505,510,529,534 %N A093028 Indices of terms in A093019 with value 8. %C A093028 Integers which require a following 8 to have a valid Luhn mod 10 check digit. %H A093028 Reinhard Zumkeller, <a href="/A093028/b093028.txt">Table of n, a(n) for n = 1..10000</a> %H A093028 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 A093028 Webopedia, <a href="http://www.webopedia.com/TERM/L/Luhn_formula.html">Luhn formula</a> %H A093028 Wikipedia, <a href="http://en.wikipedia.org/wiki/Luhn_algorithm">Luhn algorithm</a> %H A093028 <a href="/index/De#decimal_expansion">Index entries for sequences related to decimal expansion of n</a> %F A093028 A093019(a(n)) = 8. - _Reinhard Zumkeller_, Nov 08 2014 %e A093028 15 is in the sequence because A093019(15)=8; 158 has a valid Luhn mod 10 check digit. %o A093028 (Haskell) %o A093028 a093028 n = a093028_list !! (n-1) %o A093028 a093028_list = filter ((== 8) . a093019) [0..] %o A093028 -- _Reinhard Zumkeller_, Nov 08 2014 %Y A093028 Cf. A093017-A093029. %K A093028 easy,nonn,base %O A093028 1,2 %A A093028 _Ray Chandler_, Apr 03 2004 %E A093028 Offset changed by _Reinhard Zumkeller_, Nov 08 2014