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 A181109 #2 Mar 30 2012 18:57:11 %S A181109 1,1,1,1,3,1,1,5,3,1,1,7,4,3,1,1,9,5,4,3,1,1,11,7,5,4,3,1,1,13,8,7,5, %T A181109 4,3,1,1,15,10,9,7,5,4,3,1,1,17,11,11,9,7,5,4,3,1,1,19,13,12,11,9,7,5, %U A181109 4,3,1,1,21,14,13,12,11,9,7,5,4,3,1,1,23,15,15,13,13,11,9,7,5,4,3,1 %N A181109 Array whose rows result from iterating an algorithm that takes (1,1,1,1,...) to (1,3,5,7,...). %C A181109 Row 1: A000012 (constant sequence of 1's) %C A181109 Row 2: A005408 (odd positive integers) %C A181109 Row 3: A136119 %C A181109 limit-row: A003159 %F A181109 To generate row n+1 from row n, let %F A181109 (row n) = (s(1), s(2), s(3), ...) %F A181109 (row n+1) = (t(1), t(2), t(3), ...) %F A181109 Then for k=1,2,3,..., let %F A181109 t(k) = least positive integer not yet in sequences t or u %F A181109 u(k) = t(k) + s(k). %e A181109 Northwest corner: %e A181109 1...1...1...1...1....1...1....1....1... %e A181109 1...3...5...7...9...11...13...15...17... %e A181109 1...3...4...5...7...8....10...11...13... %e A181109 1...3...4...5...7...9....11...12...13... %Y A181109 Cf. A005408, A136119, A003159, A181108. %K A181109 nonn,tabl %O A181109 1,5 %A A181109 _Clark Kimberling_, Oct 03 2010