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 A190398 #14 Sep 12 2015 11:00:26
%S A190398 0,4,72,496,2100,6708,17640,40384,83376,158900,284108,482160,783484,
%T A190398 1227156,1862400,2750208,3965080,5596884,7752836,10559600,14165508,
%U A190398 18742900,24490584,31636416,40440000,51195508,64234620,79929584
%N A190398 Number of ways to place 3 nonattacking grasshoppers on a toroidal chessboard of size n x n.
%C A190398 The Grasshopper moves on the same lines as a queen, but must jump over a hurdle to land on the square immediately beyond.
%H A190398 Vincenzo Librandi, <a href="/A190398/b190398.txt">Table of n, a(n) for n = 1..1000</a>
%H A190398 V. Kotesovec, <a href="https://oeis.org/wiki/User:Vaclav_Kotesovec">Number of ways of placing non-attacking queens, kings, bishops and knights</a> (in English and Czech)
%F A190398 a(n) = 1/6*n^2*(n^4 -3*n^2 -24*n +74), n>3.
%F A190398 G.f.: -4*x^2*(3*x^8 -17*x^7 +37*x^6 -35*x^5 +11*x^4 +19*x^2 +11*x +1)/(x-1)^7.
%t A190398 CoefficientList[Series[- 4 x (3 x^8 - 17 x^7 + 37 x^6 - 35 x^5 + 11 x^4 + 19 x^2 + 11 x + 1) / (x - 1)^7, {x, 0, 50}], x] (* _Vincenzo Librandi_, Jun 02 2013 *)
%Y A190398 Cf.: A190395, A172518.
%K A190398 nonn,easy
%O A190398 1,2
%A A190398 _Vaclav Kotesovec_, May 10 2011