OFFSET
0,3
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.
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
a(n) = (2*n)!*(2*n+2)!*n / (2*n!*(n+1)!^2*(n+2)!). - Alois P. Heinz, Dec 22 2011
a(n) = Catalan(n) * binomial(2*n+1,n-1). - F. Chapoton, Nov 07 2025
MAPLE
a:= n-> (2*n)!*(2*n+2)!*n / (2*n!*(n+1)!^2*(n+2)!):
seq(a(n), n=0..20); # Alois P. Heinz, Dec 22 2011
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
EXTENSIONS
Corrected and extended by Alois P. Heinz, Dec 22 2011
STATUS
approved