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 A093019 #16 Aug 17 2021 06:49:14 %S A093019 0,8,6,4,2,9,7,5,3,1,9,7,5,3,1,8,6,4,2,0,8,6,4,2,0,7,5,3,1,9,7,5,3,1, %T A093019 9,6,4,2,0,8,6,4,2,0,8,5,3,1,9,7,5,3,1,9,7,4,2,0,8,6,4,2,0,8,6,3,1,9, %U A093019 7,5,3,1,9,7,5,2,0,8,6,4,2,0,8,6,4,1,9,7,5,3,1,9,7,5,3,0,8,6,4,2,8,6,4,2,0 %N A093019 a(n) = A093018(n) mod 10. %C A093019 Luhn mod 10 check digits of terms in A093018. %H A093019 Reinhard Zumkeller, <a href="/A093019/b093019.txt">Table of n, a(n) for n = 0..10000</a> %H A093019 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 A093019 Webopedia, <a href="http://www.webopedia.com/TERM/L/Luhn_formula.html">Luhn formula</a> %H A093019 Wikipedia, <a href="http://en.wikipedia.org/wiki/Luhn_algorithm">Luhn algorithm</a> %H A093019 <a href="/index/De#decimal_expansion">Index entries for sequences related to decimal expansion of n</a> %F A093019 a(n) = A093018(n) - 10*n. - _Reinhard Zumkeller_, Nov 08 2014 %e A093019 a(1)=8 because A093018(1) mod 10 = 18 mod 10 = 8. %e A093019 a(5)=9 because A093018(5) mod 10 = 59 mod 10 = 9. %o A093019 (Haskell) %o A093019 a093019 = flip mod 10 . a093018 -- _Reinhard Zumkeller_, Nov 08 2014 %Y A093019 Cf. A093017-A093029. %Y A093019 Cf. A010879. %K A093019 easy,nonn,base %O A093019 0,2 %A A093019 _Ray Chandler_, Apr 03 2004