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 A131968 #2 Mar 30 2012 18:57:10 %S A131968 1,3,2,6,5,4,11,10,8,7,18,17,14,13,9,29,28,23,21,15,12,42,41,35,33,25, %T A131968 20,16,61,60,51,48,37,32,26,19,86,85,71,68,54,46,38,31,22 %N A131968 Interspersion of the Farey fractal sequence, A131967. %C A131968 A permutation of the natural numbers. %D A131968 C. Kimberling, "Fractal sequences and interspersions," Ars Combinatoria 45 (1997) 157-168. %F A131968 Rectangular array T given by antidiagonals. T(i,j) = the j-th index n such that A131967(n)=i. %e A131968 Northwest corner: %e A131968 1 3 6 11 18 %e A131968 2 5 10 17 28 %e A131968 4 8 14 23 35 %e A131968 7 13 21 33 48 %Y A131968 Cf. A131967. %K A131968 nonn,tabl %O A131968 1,2 %A A131968 _Clark Kimberling_, Aug 02 2007