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 A159979 #4 Sep 08 2013 13:31:39 %S A159979 1,4,2,5,8,0,3,6,11,14,17,7,10,13,9,12,15,18,21,24,27,30,33,36,39,42, %T A159979 20,23,26,16,19,22,45,48,51,25,28,31,29,32,35,54,57,60,63,66,69,72,75, %U A159979 78,81,84,87,90,93,96,99,102,105,108,111,114,117,120,123,126,129 %N A159979 Lodumo_3 of Catalan numbers . %C A159979 Permutation of nonnegative integers. %F A159979 a(n)=lod_3(A000108(n)). %Y A159979 Cf. A000108, A039969 %K A159979 easy,nonn %O A159979 0,2 %A A159979 _Philippe Deléham_, Apr 28 2009 %E A159979 99 inserted by _R. J. Mathar_, Apr 30 2009