%I M4111
%S 1,1,1,6,15,255,1897,92263,1972653,281035054,17635484470,
%T 7490694495750,1405083604458437,1789509008288411290
%N Number of ways to halve an n X n chessboard.
%C This is the number of ways to cut an n x n chessboard along grid lines into two identical pieces. In the case that n is odd the central square is first removed to ensure an even number of squares. Solutions that differ only by rotation or reflection are considered equivalent.  _Andrew Howroyd_, Apr 19 2016
%D M. Gardner, The Unexpected Hanging and Other Mathematical Diversions. Simon and Schuster, NY, 1969, p. 189.
%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H <a href="/A003213/a003213.jpg">Illustration showing ways to quarter a 6x6 board</a>
%F a(2n) = A113900(n).  _Andrew Howroyd_, Apr 19 2016
%Y Cf. A113900, A006067, A257952, A271741.
%K nonn,nice
%O 1,4
%A _N. J. A. Sloane_.
%E a(10) corrected and a(11)a(14) from _Andrew Howroyd_, Apr 19 2016
