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 A165520 #2 Mar 30 2012 18:52:03 %S A165520 0,1,3,1,2,3,5,7,9,4,5,6,11,13,15,7,8,9,17,19,21,10,11,12,23,25,27,13, %T A165520 14,15,29,31,33 %N A165520 Antidiagonal writing from three rows trio A165351,A165355,A165367 (first,second and third trisections of A026741). %C A165520 (6n+3)-th term is 6n+3=A016945. 6n-th term is 3n=3*n=A008585. %F A165520 Mix (A004273(3n),A004273(3n+1),A004273(3n+2)), (A000027(3n),A000027(3n+1),A000027(3n+2)). %K A165520 nonn,uned %O A165520 1,3 %A A165520 _Paul Curtz_, Sep 21 2009