login
This site is supported by donations to The OEIS Foundation.

 

Logo

Annual Appeal: Please make a donation (tax deductible in USA) to keep the OEIS running. Over 5000 articles have referenced us, often saying "we discovered this result with the help of the OEIS".

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A052120 Number of 3-valent trees (= boron trees or binary trees) with n nodes. 1
1, 1, 0, 1, 0, 1, 0, 1, 0, 2, 0, 2, 0, 4, 0, 6, 0, 11, 0, 18, 0, 37, 0, 66, 0, 135, 0, 265, 0, 552, 0, 1132, 0, 2410, 0, 5098, 0, 11020, 0, 23846, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,10

COMMENTS

Trees with n nodes each of valency either 1 or 3.

LINKS

Table of n, a(n) for n=1..41.

Eric Weisstein's World of Mathematics, Cayley Tree.

Eric Weisstein's World of Mathematics, Trivalent Tree

Index entries for sequences related to trees

CROSSREFS

See A000672, the subsequence of even-numbered terms, which is the main entry for this sequence, for more terms, references, etc.

Sequence in context: A201863 A035385 A051629 * A179461 A238763 A029186

Adjacent sequences:  A052117 A052118 A052119 * A052121 A052122 A052123

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 | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified December 3 12:46 EST 2016. Contains 278734 sequences.