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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 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

REFERENCES

R. C. Mullin, On the average activity of a spanning tree of a rooted map, J. Combin. Theory, 3 (1967), 103-121.

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), 103-121. [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

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Last modified December 3 02:56 EST 2020. Contains 338899 sequences. (Running on oeis4.)