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A143891
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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 the diagonal and under 90-degree rotation.
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2
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1, 2, 1, 5, 2, 15, 7, 68, 23, 370, 104, 2649, 571, 25209, 4176, 313503, 39827, 5212881, 500254, 114569731, 8348616
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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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