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 A118816 #5 Mar 30 2012 17:31:18 %S A118816 1,0,1,1,1,0,2,2,1,3,3,1,4,4,1,5,5,0,6,6,2,7,7,2,8,8,1,9,9,3,10,10,3, %T A118816 11,11,1,12,12,4,13,13,4,14,14,1,15,15,5,16,16,5,17,17,0,18,18,6,19, %U A118816 19,6,20,20,2,21,21,7,22,22,7,23,23,2,24,24,8,25,25,8,26,26,1,27,27,9,28,28 %N A118816 A fractal sequence based upon powers of 3. %C A118816 Zeros occur at A008776, or 2*3^(k-1), k > 0. %H A118816 <a href="/index/Fo#fractal">Index entries for sequences related to "fractals"</a> %F A118816 a((3n-2)/3) = A028310(n), a((3n-1)/3) =A001477 & a(3n)=a(n), thus this sequence is a fractal. %t A118816 a[1] = 1; a[n_] := Switch[ Mod[n, 3], 0, a[n/3], 1, (n - 1)/3, 2, (n - 2)/3]; Array[a, 90] %Y A118816 Cf. A003602, A101279. %K A118816 nonn %O A118816 1,7 %A A118816 _Robert G. Wilson v_, May 23 2006