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 A263623 #18 Dec 26 2024 03:46:08 %S A263623 1,2,4,8,36 %N A263623 a(1)=1; thereafter, a(n) = smallest k such that the decimal concatenation [a(n-2)+1 a(n-2)+2, ... a(n-1)] divides the decimal concatenation [a(n-1)+1 a(n-1)+2 ... k]. %C A263623 a(6), if it exists, is > 10^6. - _Lars Blomberg_, Dec 01 2016 %C A263623 a(6) <= 86794654347484748866500883685475458354620023089553379437308257589024531796179370608623026912768. - _Max Alekseyev_, Dec 25 2024 %e A263623 n=3: a(3) = 4 because k=4 is the smallest number such that 2 divides the concatenation 345...k. %e A263623 n=4: a(4) = 8 because k=8 is the smallest number such that 34 divides the concatenation 567...k. See A002782 for the relevant concatenations. %Y A263623 Cf. A002782, A029455, A332580. %K A263623 nonn,base,hard,more %O A263623 1,2 %A A263623 _N. J. A. Sloane_, Oct 23 2015