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 A105159 #10 Sep 08 2013 19:54:50 %S A105159 1,1,1,3,3,3,3,3,3,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,3,1,9,1,9,3, %T A105159 1,9,3,1,9,3,1,9,3,1,9,3,1,9,3,1,9,3,1 %N A105159 Consider trajectory of n under repeated application of map k --> A105108(k); a(n) = length of cycle. %C A105159 Why is this always a power of 3? %H A105159 David Applegate, Benoit Cloitre, Philippe Deléham and N. J. A. Sloane, Sloping binary numbers: a new sequence related to the binary numbers [<a href="http://neilsloane.com/doc/slopey.pdf">pdf</a>, <a href="http://neilsloane.com/doc/slopey.ps">ps</a>]. %Y A105159 Cf. A102370, A105108, A105154. %K A105159 nonn,base %O A105159 0,4 %A A105159 _Philippe Deléham_, Apr 30 2005