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 A061971 #14 Mar 09 2020 22:00:01
%S A061971 1,17,89,6343,9707,9799,91069,120581,484307,725341,2571749,3432583,
%T A061971 4482203
%N A061971 Numbers n such that n divides the (left) concatenation of all numbers <= n written in base 18 (most significant digit on right).
%C A061971 This sequence differs from A029535 in that all least significant zeros are kept during concatenation.
%C A061971 No more terms < 8*10^6.
%H A061971 <a href="/index/N#concat">Index entries for related sequences</a>
%e A061971 See A061955 for example.
%t A061971 b = 18; c = {}; Select[Range[10^4], Divisible[FromDigits[c = Join[Reverse[IntegerDigits[#, b]], c], b], #] &] (* _Robert Price_, Mar 09 2020 *)
%Y A061971 Cf. A029447-A029470, A029471-A029494, A029495-A029518, A029519-A029542, A061931-A061954, A061955-A061978.
%K A061971 nonn,base,more
%O A061971 1,2
%A A061971 Larry Reeves (larryr(AT)acm.org), May 24 2001 a(9)-a(13) from
%E A061971 Edited and updated by Larry Reeves (larryr(AT)acm.org), Apr 12 2002
%E A061971 a(9)-a(13) from _Lars Blomberg_, Aug 02 2011