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A143884
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Number of ways of placing kings with no more than 3 mutual attacks on an n X n chessboard symmetric about both diagonal and antidiagonal.
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1
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1, 2, 3, 7, 16, 41, 121, 434, 1581, 7325, 35854, 219307, 1397579, 11370922
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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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