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 A097290 #3 Mar 30 2012 18:57:05 %S A097290 1,2,3,5,4,6,8,11,7,9,13,16,12,10,14,18,21,23,17,15,19,25,28,30,24,22, %T A097290 20,26,32,35,37,39,31,29,27,33,41,44,46,48,40,38,36,34,42,50,53,55,57, %U A097290 59,49,47,45,43,51,61,64,66,68,70,60,58,56,54,52,62,72,75,77,79,81,83 %N A097290 Rectangular array T, by antidiagonals: T(n,k) = rank of k-th n in A097289. %C A097290 As a sequence this is a permutation of the natural numbers. %e A097290 Northwest corner: %e A097290 1 2 5 8 %e A097290 3 4 11 16 %e A097290 6 7 12 23 %e A097290 9 10 17 24 %Y A097290 Cf. A098289. %K A097290 nonn,tabl %O A097290 1,2 %A A097290 _Clark Kimberling_, Aug 05 2004