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 A061939 #17 Dec 05 2020 06:36:02
%S A061939 1,2,3,5,6,9,99,153,189,238,252,323,444,539,927,3099,3753,4224,5451,
%T A061939 8967,44544,53673,97119,1423719,3860793,4773591
%N A061939 Numbers n such that n divides the (right) concatenation of all numbers <= n written in base 10 (most significant digit on right).
%C A061939 This sequence differs from A029503 in that all least significant zeros are removed before concatenation.
%C A061939 No more terms < 10^7. - _Lars Blomberg_, Oct 20 2011
%H A061939 <a href="/index/N#concat">Index entries for related sequences</a>
%e A061939 See A061931 for example.
%t A061939 b = 10; c = {}; Select[Range[10^4], Divisible[FromDigits[c = Join[c, IntegerDigits[IntegerReverse[#, b], b]], b], #] &] (* _Robert Price_, Mar 08 2020 *)
%o A061939 (PARI) lista(nn, m=10) = my(s, t); for(k=1, nn, s=k/m^valuation(k, m); while(s, t=t*m+s%m; s\=m); if(t%k==0, print1(k, ", "))); \\ _Jinyuan Wang_, Dec 05 2020
%Y A061939 Cf. A029447-A029470, A029471-A029494, A029495-A029518, A029519-A029542, A061931-A061954, A061955-A061978.
%K A061939 nonn,base,more
%O A061939 1,2
%A A061939 Larry Reeves (larryr(AT)acm.org), May 24 2001
%E A061939 Edited and updated by Larry Reeves (larryr(AT)acm.org), Apr 12 2002
%E A061939 a(24)-a(26) from _Lars Blomberg_, Oct 20 2011