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A082989 Number of ordered trees with n edges and having no root-to-leaf branches. 3
1, 0, 0, 1, 4, 13, 42, 139, 470, 1616, 5632, 19852, 70654, 253559, 916558, 3334211, 12197142, 44842184, 165597008, 613991206, 2284809072, 8530458154, 31945128628, 119960276246, 451621453764, 1704240175868, 6445111657272 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,5

LINKS

Table of n, a(n) for n=0..26.

FORMULA

a(n) = 2*sum((-1)^j*(j+2)*C(2n-3-2j,n), j=0..floor((n-3)/2))/(n+1).

G.f.: 2(1-z)/[1+z+(1-z)sqrt(1-4z)].

CROSSREFS

Sequence in context: A010900 A175005 A070031 * A267240 A192802 A149425

Adjacent sequences:  A082986 A082987 A082988 * A082990 A082991 A082992

KEYWORD

nonn

AUTHOR

Emeric Deutsch, May 29 2003

STATUS

approved

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Last modified June 5 23:10 EDT 2020. Contains 334858 sequences. (Running on oeis4.)