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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; internal format)
OFFSET

0,5

FORMULA

a(n)=2sum((-1)^j*(j+2)binomial(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 * A192802 A149425 A047144

Adjacent sequences:  A082986 A082987 A082988 * A082990 A082991 A082992

KEYWORD

nonn

AUTHOR

Emeric Deutsch (deutsch(AT)duke.poly.edu), May 29 2003

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Last modified February 15 16:56 EST 2012. Contains 205825 sequences.