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 A029503 #24 Mar 12 2020 21:53:20
%S A029503 1,2,3,5,6,9,101,107,153,167,277,414,486,858,1659,2894,3093,4299,4842,
%T A029503 8838,22734,31869,69492,361057,429786,462018,859002,1170801,1334667,
%U A029503 1663923,6143512,6162396,6212646,7034661,8164443
%N A029503 Numbers n such that n divides the (right) concatenation of all numbers <= n written in base 10 (most significant digit on right).
%C A029503 This sequence differs from A061939 in that all least significant zeros are kept during concatenation.
%C A029503 Right concatenation, reverse order.
%C A029503 No more terms < 10^7. - _Lars Blomberg_, Oct 06 2011
%H A029503 <a href="/index/N#concat">Index entries for related sequences</a>
%e A029503 n = 22 is not a term since 12345678901112131415161718191021222 is not divisible by 22.
%e A029503 See A029495 for other examples.
%t A029503 b = 10; c = {}; Select[Range[10^4], Divisible[FromDigits[c = Join[c, Reverse[IntegerDigits[#, b]]], b], #] &] (* _Robert Price_, Mar 12 2020 *)
%o A029503 (PARI) isok(n) = my(s = ""); for (k=1, n, sk = digits(k); forstep (j=#sk, 1, -1, s = concat(s, sk[j]))); (eval(s) % n) == 0; \\ _Michel Marcus_, Jan 28 2017
%Y A029503 Cf. A029447-A029470, A029471-A029494, A029495-A029518, A029519-A029542, A061931-A061954, A061955-A061978.
%K A029503 nonn,base,more
%O A029503 1,2
%A A029503 _Olivier Gérard_
%E A029503 Edited and updated by Larry Reeves (larryr(AT)acm.org), Apr 12 2002
%E A029503 Additional comments and more terms from Larry Reeves (larryr(AT)acm.org), May 25 2001
%E A029503 a(25)-a(35) from _Lars Blomberg_, Oct 06 2011