Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #25 Jun 30 2024 01:42:47
%S 1,5,25,43,55,128,275,1280,2816,5888,6400,12800,28160,33413,37376,
%T 129919,140800,286025,352000,990845,1050880,1773725,2848000,3581033,
%U 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 Numbers k that divide the (left) concatenation of all numbers <= k written in base 21 (most significant digit on left).
%C a(62) > 3*10^10. - _Jason Yuen_, Jun 29 2024
%H Jason Yuen, <a href="/A029490/b029490.txt">Table of n, a(n) for n = 1..61</a>
%H <a href="/index/N#concat">Index entries for related sequences</a>
%t b = 21; c = {}; Select[Range[10^4], Divisible[FromDigits[c = Join[IntegerDigits[#, b], c], b], #] &] (* _Robert Price_, Mar 12 2020 *)
%Y Cf. A029447-A029470, A029471-A029494, A029495-A029518, A029519-A029542, A061931-A061954, A061955-A061978.
%K nonn,base
%O 1,2
%A _Olivier Gérard_
%E More terms from Andrew Gacek (andrew(AT)dgi.net), Feb 21 2000
%E More terms from Larry Reeves (larryr(AT)acm.org), May 24 2001
%E Edited and updated by Larry Reeves (larryr(AT)acm.org), Apr 12 2002
%E a(20)-a(49) from _Max Alekseyev_, May 15 2011