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 A004284 #8 Dec 22 2012 15:14:57
%S A004284 1,10,111,10,11,1110,111,100,1101,110,11111,1110,1001,1110,111111,100,
%T A004284 101,11010,100111,110,111,111110,1011,11100,11011,10010,1101,1110,
%U A004284 10011,1111110,11111,1000,101001,1010,111111,11010,1001111
%N A004284 Least positive multiple of n written in base 4 using only 0 and 1.
%H A004284 Harvey P. Dale, <a href="/A004284/b004284.txt">Table of n, a(n) for n = 1..200</a>
%t A004284 lpm4[n_]:=Module[{k=1},While[Rest[Most[DigitCount[n k,4]]]!={0,0},k++]; FromDigits[IntegerDigits[n k,4]]]; Array[lpm4,40] (* _Harvey P. Dale_, Dec 22 2012 *)
%K A004284 nonn,base
%O A004284 1,2
%A A004284 _David W. Wilson_