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A189868
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Number of ways to place n nonattacking composite pieces queen + leaper[2,4] on an n X n chessboard.
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2
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1, 0, 0, 2, 0, 0, 0, 0, 0, 4, 64, 384, 2936, 10720, 62664, 420272, 2540584, 16373760, 115200080, 868564232, 6708291360
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OFFSET
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1,4
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COMMENTS
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a(n) is also number of permutations p of 1,2,...,n satisfying |p(i+2)-p(i)|<>4 AND |p(j+4)-p(j)|<>2 AND |p(m+k)-p(m)|<>k for all i>=1, j>=1, m>=1, k>=1, i+2<=n, j+4<=n, m+k<=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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