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 A181398 #6 Jan 08 2020 17:50:00 %S A181398 0,4,64,1912,148432,32871240,20744801272,37559607987584, %T A181398 198461813970383240,3100218604533034920976, %U A181398 144170284249598867501946128,20038589080922552365824887715432,8349298401437323416105571304163524760,10453318954664242363219930783045003561923656 %N A181398 Summed lengths of nonintersecting rook paths on an n X n board. %C A181398 Paths are self-avoiding from one corner to the diagonally opposite corner. %e A181398 For 2 x 2: right+down (length 2), down+right (length 2), s(2) = 2+2 = 4 %Y A181398 Main diagonal of A181399. %Y A181398 Related sequences A181394, A181395, A181396, A181397. %K A181398 nonn %O A181398 1,2 %A A181398 _David Scambler_, Oct 17 2010 %E A181398 a(7)-a(14) from _Andrew Howroyd_, Jan 07 2020