OFFSET
2,2
REFERENCES
C. Chauve, S. Dulucq and O. Guibert, Enumeration of some labeled trees, research report RR-1226-99, LaBRI, Bordeaux I University, 1999.
LINKS
C. Chauve, S. Dulucq and O. Guibert, Enumeration of some labelled trees, FPSAC 2000, pp. 146-157. 2000.
FORMULA
From Vladimir Kruchinin, Jun 02 2016: (Start)
E.g.f.: -[(log(1-x*C(x)))/C(x)]', where C(x) is g.f. of Catalan numbers (A000108).
a(n) = ((n+1)!*Sum_{k=1..n} ((k*binomial(2*n-k-1,n-k))/(k+1)))/n. (End)
MAPLE
a:= n -> ((2*n-2)! / (n-1)!) - sum((n+k-1)! / ((n-k-1)*k!), k=0 .. n-2):
seq(a(n), n=2..22);
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Cedric Chauve (chauve(AT)lacim.uqam.ca), May 16 2002
STATUS
approved