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 A181399 #21 Jan 08 2020 17:48:57 %S A181399 0,1,1,2,4,2,3,14,14,3,4,40,64,40,4,5,104,284,284,104,5,6,256,1206, %T A181399 1912,1206,256,6,7,608,4882,13132,13132,4882,608,7,8,1408,19060,88608, %U A181399 148432,88608,19060,1408,8,9,3200,72588,577727,1692480,1692480,577727,72588,3200,9 %N A181399 Summed lengths of nonintersecting rook paths on an n X k board (square array by antidiagonals). %C A181399 Paths are self-avoiding from one corner to the diagonally opposite corner. %H A181399 Andrew Howroyd, <a href="/A181399/b181399.txt">Table of n, a(n) for n = 1..378</a> (terms 1..66 from David Scambler) %e A181399 Array starts: %e A181399 ====================================================== %e A181399 n\k| 1 2 3 4 5 6 7 %e A181399 ---|-------------------------------------------------- %e A181399 1 | 0 1 2 3 4 5 6 ... %e A181399 2 | 1 4 14 40 104 256 608 ... %e A181399 3 | 2 14 64 284 1206 4882 19060 ... %e A181399 4 | 3 40 284 1912 13132 88608 577727 ... %e A181399 5 | 4 104 1206 13132 148432 1692480 18893254 ... %e A181399 6 | 5 256 4882 88608 1692480 32871240 ... %e A181399 7 | 6 608 19060 577727 18893254 ... %e A181399 ... %Y A181399 Related sequences: A181394 (3 X n), A181395 (4 X n), A181396 (5 X n), A181397 (6 X n), A181398 (n X n). %Y A181399 The number of these paths is given in A064298. %K A181399 nonn,tabl %O A181399 1,4 %A A181399 _David Scambler_, Oct 17 2010 %E A181399 a(55) and a(60) in b-file corrected by _Andrew Howroyd_, Feb 23 2018