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A189862
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Number of ways to place n nonattacking composite pieces rook + rider[4,6] on an n X n chessboard.
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1
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1, 2, 6, 24, 120, 720, 3720, 22336, 153796, 1213344, 10849504, 108891704, 1023690268, 10593791168, 119694887008, 1472935989952
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OFFSET
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1,2
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COMMENTS
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a(n) is also number of permutations p of 1,2,...,n satisfying |p(i+4k)-p(i)|<>6k AND |p(j+6k)-p(j)|<>4k for all i>=1, j>=1, k>=1, i+4k<=n, j+6k<=n
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CROSSREFS
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KEYWORD
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nonn,hard
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AUTHOR
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STATUS
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approved
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