A029538 - OEIS

A029538

Numbers n such that n divides the (left) concatenation of all numbers <= n written in base 21 (most significant digit on right and removing all least significant zeros before concatenation).

%I #22 Jan 13 2025 13:24:25

%S 1,5,40,65,80,928,1504,4568,4640,4880,5065,11201,31145,40555,89480,

%T 812645,1281320

%N Numbers n such that n divides the (left) concatenation of all numbers <= n written in base 21 (most significant digit on right and removing all least significant zeros before concatenation).

%C This sequence differs from A061974 in that all least significant zeros are removed before concatenation.

%C No more terms < 10^7. [_Lars Blomberg_, Sep 26 2011]

%H <a href="/index/N#concat">Index entries for related sequences</a>

%e See A029519 for example.

%t b = 21; c = {}; Select[Range[10^4], Divisible[FromDigits[c = Join[IntegerDigits[IntegerReverse[#, b], b], c], b], #] &] (* _Robert Price_, Mar 13 2020 *)

%Y Cf. A029447-A029470, A029471-A029494, A029495-A029518, A029519-A029542, A061931-A061954, A061955-A061978.

%K nonn,base,more

%O 1,2

%A _Olivier Gérard_

%E Edited and updated by Larry Reeves (larryr(AT)acm.org), Apr 12 2002

%E Additional comments and more terms from Larry Reeves (larryr(AT)acm.org), May 25 2001

%E a(16)-a(17) from _Lars Blomberg_, Sep 26 2011