%I A037026
%S A037026 0,1,1,1,2,2,4,5,9,15,28,45,73,116,199,345,601,1021,1738,2987,5244,
%T A037026 9321,16720,30103,54345,97996,176011,314045,556577,980852,1722451,
%U A037026 3020214,5298570,9316456,16440262,29136489,51860214,92643425,165934156
%N A037026 B-trees of order 4 with n leaves.
%H A037026 Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/
               B-Tree.html">Link to a section of The World of Mathematics.</a>
%H A037026 <a href="Sindx_Ro.html#rooted">Index entries for sequences related to 
               rooted trees</a>
%p A037026 spec := [ B, {B=Union(Z, Subst(M, B)), M=Union(Prod(Z,Z),Prod(Z,Z,Z),
               Prod(Z$4))} ]: [ seq(combstruct[count](spec, size=n), n=0..42) ];
%Y A037026 Cf. A014535.
%Y A037026 Sequence in context: A050192 A007147 A127968 this_sequence A116651 A135586 
               A116646
%Y A037026 Adjacent sequences: A037023 A037024 A037025 this_sequence A037027 A037028 
               A037029
%K A037026 nonn
%O A037026 0,5
%A A037026 N. J. A. Sloane (njas(AT)research.att.com), Paul.Zimmermann(AT)loria.fr