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Numbers k that divide the (right) concatenation of all numbers <= k written in base 21 (most significant digit on left).
2

%I #12 Jul 04 2021 01:58:03

%S 1,3,5,7,15,21,25,35,45,48,49,63,75,79,80,105,112,144,147,175,203,225,

%T 240,245,295,315,327,336,369,400,441,525,560,675,720,735,784,805,945,

%U 1008,1029,1113,1200,1225,1267,1323,1392,1575,1680,1715,1953,2043

%N Numbers k that divide the (right) concatenation of all numbers <= k written in base 21 (most significant digit on left).

%H Robert Price, <a href="/A029466/b029466.txt">Table of n, a(n) for n = 1..137</a>

%t b = 21; c = {}; Select[Range[10^5], Divisible[FromDigits[c = Join[c, IntegerDigits[#, b]], b], #] &] (* _Robert Price_, Mar 11 2020 *)

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

%K nonn,base

%O 1,2

%A _Olivier GĂ©rard_