login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A029766 Unary-binary rooted trees with n nodes. 0
0, 1, 2, 12, 48, 360, 2160, 25200, 201600, 2540160, 25401600, 399168000, 4790016000, 80951270400, 1133317785600, 23538138624000, 376610217984000, 8180810846208000, 147254595231744000, 3649353012264960000 (list; graph; refs; listen; history; text; internal format)
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 A338522 A277183

Adjacent sequences:  A029763 A029764 A029765 * A029767 A029768 A029769

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified January 18 04:26 EST 2022. Contains 350410 sequences. (Running on oeis4.)