%I A052525
%S A052525 0,0,0,1,1,2,3,6,10,20,36,71,136,270,531,1070,2147,4367,8895,18262,
%T A052525 37588,77795,161444,336383,702732,1472582,3093151,6513402,13744384,
%U A052525 29063588,61570853,130669978,277767990,591373581,1260855164
%N A052525 Number of unlabeled rooted trees with n leaves in which the degrees of 
               the root and all internal nodes are >= 3.
%C A052525 Old name was "Non-planar 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 (njas(AT)research.att.com).
%H A052525 INRIA Algorithms Project, <a href="http://algo.inria.fr/bin/encyclopedia?Search=ECSnb&argsearch=95">
               Encyclopedia of Combinatorial Structures 95</a>
%e A052525 For instance, with 7 leaves, the 6 choices are:
%e A052525 . [ *,*,*,*,*,*,* ]
%e A052525 . [ *,*,*,*,[ *,*,* ] ]
%e A052525 . [ *,*,*,[ *,*,*,* ] ]
%e A052525 . [ *,*,[ *,*,*,*,* ] ]
%e A052525 . [ *,*,[ *,*,[ *,*,* ] ] ]
%e A052525 . [ *,[ *,*,* ],[ *,*,* ] ]
%p A052525 spec := [ S, {B=Union(S, Z), S=Set(B, 3 <= card)}, unlabeled ]: seq(combstruct[ 
               count ](spec, size=n), n=0..50);
%Y A052525 Cf. A052524 and A052526.
%Y A052525 Sequence in context: A036557 A047131 A008927 this_sequence A006606 A120421 
               A005418
%Y A052525 Adjacent sequences: A052522 A052523 A052524 this_sequence A052526 A052527 
               A052528
%K A052525 easy,nonn
%O A052525 0,6
%A A052525 encyclopedia(AT)pommard.inria.fr, Jan 25 2000
%E A052525 More terms from Paul.Zimmermann(AT)loria.fr, Oct 31 2002