%I
%S 0,0,0,1,1,2,3,6,10,20,36,71,136,270,531,1070,2147,4367,8895,18262,
%T 37588,77795,161444,336383,702732,1472582,3093151,6513402,13744384,
%U 29063588,61570853,130669978,277767990,591373581,1260855164
%N Number of unlabeled rooted trees with n leaves in which the degrees of the root and all internal nodes are >= 3.
%C Old name was "Nonplanar unlabeled trees with neither unary nor binary nodes". I am leaving this alternative name here because it may help clarify the definitions of related sequences.  _N. J. A. Sloane_.
%H Vaclav Kotesovec, <a href="/A052525/b052525.txt">Table of n, a(n) for n = 0..1000</a>
%H INRIA Algorithms Project, <a href="http://ecs.inria.fr/services/structure?nbr=95">Encyclopedia of Combinatorial Structures 95</a>
%F a(n) ~ c * d^n / n^(3/2), where d = 2.2318799173898687960533559522113115638..., c = 0.3390616344584879699709248904124... .  _Vaclav Kotesovec_, May 04 2015
%e For instance, with 7 leaves, the 6 choices are:
%e . [ *,*,*,*,*,*,* ]
%e . [ *,*,*,*,[ *,*,* ] ]
%e . [ *,*,*,[ *,*,*,* ] ]
%e . [ *,*,[ *,*,*,*,* ] ]
%e . [ *,*,[ *,*,[ *,*,* ] ] ]
%e . [ *,[ *,*,* ],[ *,*,* ] ]
%p spec := [ S, {B=Union(S, Z), S=Set(B, 3 <= card)}, unlabeled ]: seq(combstruct[ count ](spec, size=n), n=0..50);
%Y Cf. A052524 and A052526.
%K easy,nonn
%O 0,6
%A encyclopedia(AT)pommard.inria.fr, Jan 25 2000
%E More terms from _Paul Zimmermann_, Oct 31 2002
