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A143890
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Number of ways of placing kings with no more than 4 mutual attacks on an n X n chessboard symmetric about both diagonal and antidiagonal.
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2
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1, 2, 3, 9, 16, 61, 143, 802, 2265, 17236, 59156, 631443, 2686969, 39237301, 210001256
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OFFSET
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0,2
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LINKS
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CROSSREFS
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KEYWORD
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nonn,more,hard
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AUTHOR
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STATUS
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approved
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