%I
%S 1,7,104,3970,431932,137066448,128095791922,355704307903818,
%T 2952926822418475378,73569487283165427567144,
%U 5515501712040561162370942752,1246743475892797935712690352483842,850999652841310762943520023896881419780
%N Number of ways to quarter a 2n+1 X 2n+1 chessboard with central square removed.
%C The chessboard must be dissected into four identical pieces. All solutions have 90 degree rotational symmetry and solutions that differ only by rotation or reflection are considered equivalent.
%F a(n) = A006067(2*n+1).
%t A006067 = Import["https://oeis.org/A006067/b006067.txt", "Table"][[All, 2]];
%t a[n_] := A006067[[2n+1]];
%t a /@ Range[1, 13] (* _JeanFrançois Alcover_, Sep 14 2019 *)
%Y Cf. A006067, A064941, A257952.
%K nonn
%O 1,2
%A _Andrew Howroyd_, Apr 19 2016
