A046715 - OEIS

%I #21 May 19 2024 14:03:09

%S 0,1,10,105,1176,13860,169884,2147145,27810640,367479684,4936848280,

%T 67255063876,927192688800,12914469594000,181497968832600,

%U 2570903476583625,36671501616314400,526348636137670500,7597019633665077000,110205019733436728100

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

%H Alois P. Heinz, <a href="/A046715/b046715.txt">Table of n, a(n) for n = 0..250</a>

%H R. C. Mullin, <a href="http://dx.doi.org/10.1016/S0021-9800(67)80001-2">On the average activity of a spanning tree of a rooted map</a>, J. Combin. Theory, 3 (1967), 103-121.

%H R. C. Mullin, <a href="/A260039/a260039.pdf">On the average activity of a spanning tree of a rooted map</a>, J. Combin. Theory, 3 (1967), 103-121. [Annotated scanned copy]

%F B(n) = (2*n)!*(2*n+2)!*n / (2*n!*(n+1)!^2*(n+2)!). - _Alois P. Heinz_, Dec 22 2011

%p B:= n-> (2*n)!*(2*n+2)!*n / (2*n!*(n+1)!^2*(n+2)!):

%p seq(B(n), n=0..20); # _Alois P. Heinz_, Dec 22 2011

%K nonn,easy

%O 0,3

%A _N. J. A. Sloane_

%E Corrected and extended by _Alois P. Heinz_, Dec 22 2011