

A046715


Secondary root edges in doubly rooted tree maps with n edges.


2



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

0,3


REFERENCES

R. C. Mullin, On the average activity of a spanning tree of a rooted map, J. Combin. Theory, 3 (1967), 103121.


LINKS

Alois P. Heinz, Table of n, a(n) for n = 0..250
R. C. Mullin, On the average activity of a spanning tree of a rooted map, J. Combin. Theory, 3 (1967), 103121. [Annotated scanned copy]


FORMULA

B(n) = (2*n)!*(2*n+2)!*n / (2*n!*(n+1)!^2*(n+2)!).  Alois P. Heinz, Dec 22 2011


MAPLE

B:= n> (2*n)!*(2*n+2)!*n / (2*n!*(n+1)!^2*(n+2)!):
seq(B(n), n=0..20); # Alois P. Heinz, Dec 22 2011


CROSSREFS

Sequence in context: A163166 A068767 A233830 * A145713 A123512 A079515
Adjacent sequences: A046712 A046713 A046714 * A046716 A046717 A046718


KEYWORD

nonn,easy


AUTHOR

N. J. A. Sloane


EXTENSIONS

Corrected and extended by Alois P. Heinz, Dec 22 2011


STATUS

approved



