

A003155


Number of ways to halve an n X n chessboard.
(Formerly M4111)


0



1, 1, 1, 6, 15, 255, 1897, 92263, 1972653, 281035054, 17635484470, 7490694495750, 1405083604458437, 1789509008288411290
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OFFSET

1,4


COMMENTS

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


REFERENCES

M. Gardner, The Unexpected Hanging and Other Mathematical Diversions. Simon and Schuster, NY, 1969, p. 189.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).


LINKS

Table of n, a(n) for n=1..14.
Illustration showing ways to quarter a 6x6 board


FORMULA

a(2n) = A113900(n).  Andrew Howroyd, Apr 19 2016


CROSSREFS

Cf. A113900, A006067, A257952, A271741.
Sequence in context: A013230 A306342 A117062 * A199095 A235230 A024081
Adjacent sequences: A003152 A003153 A003154 * A003156 A003157 A003158


KEYWORD

nonn,nice


AUTHOR

N. J. A. Sloane.


EXTENSIONS

a(10) corrected and a(11)a(14) from Andrew Howroyd, Apr 19 2016


STATUS

approved



