A029766 Unary-binary rooted trees with n nodes.

0, 1, 2, 12, 48, 360, 2160, 25200, 201600, 2540160, 25401600, 399168000, 4790016000, 80951270400, 1133317785600, 23538138624000, 376610217984000, 8180810846208000, 147254595231744000, 3649353012264960000

Offset

0,3

Comments

A unary-binary tree is simply a tree in which every node has degree <= 3.

Conjecture: for n > 0, a(n) = n! * A040039(n-1). - Vaclav Kotesovec, Sep 30 2013

References

F. Bergeron, G. Labelle and P. Leroux, Combinatorial Species and Tree-Like Structures, Camb. 1998, p. 254.

Links

Table of n, a(n) for n=0..19.

Index entries for sequences related to rooted trees

Formula

E.g.f.: (1-x-sqrt(1-2x-3x^2))/(2x). [Incorrect, this is the o.g.f. for A001006, Joerg Arndt, Oct 02 2013]

Crossrefs

Sequence in context: A221663 A232663 A052591 * A088311 A359118 A338522

Adjacent sequences: A029763 A029764 A029765 * A029767 A029768 A029769

Keyword

nonn,easy

Author

N. J. A. Sloane

Status

approved