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A046715
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Secondary root edges in doubly rooted tree maps with n edges.
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2
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0, 1, 10, 105, 1176, 13860, 169884, 2147145, 27810640, 367479684, 4936848280, 67255063876, 927192688800, 12914469594000, 181497968832600, 2570903476583625, 36671501616314400, 526348636137670500, 7597019633665077000, 110205019733436728100
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OFFSET
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0,3
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REFERENCES
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R. C. Mullin, On the average activity of a spanning tree of a rooted map, J. Combin. Theory, 3 (1967), 103-121.
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LINKS
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FORMULA
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B(n) = (2*n)!*(2*n+2)!*n / (2*n!*(n+1)!^2*(n+2)!). - Alois P. Heinz, Dec 22 2011
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MAPLE
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B:= n-> (2*n)!*(2*n+2)!*n / (2*n!*(n+1)!^2*(n+2)!):
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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