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 A029490 #25 Jun 30 2024 01:42:47
%S A029490 1,5,25,43,55,128,275,1280,2816,5888,6400,12800,28160,33413,37376,
%T A029490 129919,140800,286025,352000,990845,1050880,1773725,2848000,3581033,
%U A029490 4343680,4428160,5624960,6732160,7553920,8497280,9249995,9872000,10938752,11426176,14558575,14569600,15368320,18998705,19312000,21362275,24208000,24934855,27632000,32432000,37022605,43193216,51382265,53717375,81016375
%N A029490 Numbers k that divide the (left) concatenation of all numbers <= k written in base 21 (most significant digit on left).
%C A029490 a(62) > 3*10^10. - _Jason Yuen_, Jun 29 2024
%H A029490 Jason Yuen, <a href="/A029490/b029490.txt">Table of n, a(n) for n = 1..61</a>
%H A029490 <a href="/index/N#concat">Index entries for related sequences</a>
%t A029490 b = 21; c = {}; Select[Range[10^4], Divisible[FromDigits[c = Join[IntegerDigits[#, b], c], b], #] &] (* _Robert Price_, Mar 12 2020 *)
%Y A029490 Cf. A029447-A029470, A029471-A029494, A029495-A029518, A029519-A029542, A061931-A061954, A061955-A061978.
%K A029490 nonn,base
%O A029490 1,2
%A A029490 _Olivier Gérard_
%E A029490 More terms from Andrew Gacek (andrew(AT)dgi.net), Feb 21 2000
%E A029490 More terms from Larry Reeves (larryr(AT)acm.org), May 24 2001
%E A029490 Edited and updated by Larry Reeves (larryr(AT)acm.org), Apr 12 2002
%E A029490 a(20)-a(49) from _Max Alekseyev_, May 15 2011