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 A061933 #26 Feb 03 2025 13:43:32
%S A061933 1,2,3,9,15,21,162,495,614,813,174913,240389,704162
%N A061933 Numbers n such that n divides the (right) concatenation of all numbers <= n written in base 4 (most significant digit on right, least significant zeros not written).
%C A061933 This sequence differs from A029497 in that all least significant zeros are removed before concatenation.
%C A061933 The next term is > 400000. - _Larry Reeves_, Jan 16 2002
%C A061933 Next term exceeds 10000000. - _Sean A. Irvine_, Sep 03 2009
%H A061933 <a href="/index/N#concat">Index entries for related sequences</a>
%e A061933 See A061931 for example.
%t A061933 b = 4; c = {}; Select[Range[10^4], Divisible[FromDigits[
%t A061933 c = Join[c, IntegerDigits[IntegerReverse[#, b], b]], b], #] &] (* _Robert Price_, Mar 07 2020 *)
%o A061933 (PARI) lista(nn, m=4) = my(s, t); for(k=1, nn, s=k/m^valuation(k, m); while(s, t=t*m+s%m; s\=m); if(t%k==0, print1(k, ", "))); \\ _Jinyuan Wang_, Dec 05 2020
%Y A061933 Cf. A029447-A029470, A029471-A029494, A029495-A029518, A029519-A029542, A061931-A061954, A061955-A061978.
%K A061933 nonn,base,more
%O A061933 1,2
%A A061933 Larry Reeves (larryr(AT)acm.org), May 24 2001
%E A061933 Edited and updated by Larry Reeves (larryr(AT)acm.org), Apr 12 2002
%E A061933 a(13) from _Sean A. Irvine_, Sep 03 2009