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 A003155 Number of ways to halve an n X n chessboard. (Formerly M4111) 1
 1, 1, 1, 6, 15, 255, 1897, 92263, 1972653, 281035054, 17635484470, 7490694495750, 1405083604458437, 1789509008288411290 (list; graph; refs; listen; history; text; internal format)
 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 * A335578 A199095 A235230 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

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Last modified December 2 03:35 EST 2023. Contains 367505 sequences. (Running on oeis4.)