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A189863
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Number of ways to place n nonattacking composite pieces rook + rider[5,6] on an n X n chessboard.
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0
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1, 2, 6, 24, 120, 720, 4176, 26140, 185084, 1491098, 13285034, 132514356, 1321161252, 14181339764, 164574628260, 2057033314380
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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+5k)-p(i)|<>6k AND |p(j+6k)-p(j)|<>5k for all i>=1, j>=1, k>=1, i+5k<=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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