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 A166720 #5 May 01 2013 21:13:45 %S A166720 0,3,3,9,12,15,9,21,6,27,15,33,18,39,21,45,12,51,27,57,240,63,33,69, %T A166720 18,75,39,81,42,87,45,93,24,99,51,105,108,111,57,117,30,123,63,129,66, %U A166720 135,69,141,36,147,75,153,312,159 %N A166720 Trisection A165342(3n). %F A166720 See A165351 from A026741. %K A166720 nonn %O A166720 0,2 %A A166720 _Paul Curtz_, Oct 20 2009 %E A166720 Edited by _N. J. A. Sloane_, Oct 22 2009