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

 

Logo

Thanks to everyone who made a donation during our annual appeal!
To see the list of donors, or make a donation, see the OEIS Foundation home page.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A124973 a(n) = Sum_{0 <= k < n/2} a(k)a(n-1-k), with a(0) = a(1) = 1. 2
1, 1, 1, 1, 2, 3, 6, 11, 22, 42, 87, 174, 365, 745, 1587, 3303, 7103, 14974, 32477, 69284, 151172, 325077, 713400, 1545719, 3406989, 7423648, 16429555, 35992438, 79912474, 175785514, 391488688, 864591621, 1930333822, 4276537000 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,5

COMMENTS

Number of unordered rooted trees with all outdegrees <= 2 and, if a node has two subtrees, they have a different number of nodes (equivalently, ordered rooted trees where the left subtree has more nodes than the right subtree).

LINKS

Table of n, a(n) for n=0..33.

CROSSREFS

Cf. A000992, A001190, A032305, A000108.

Sequence in context: A141072 A043328 A002083 * A318123 A226594 A043327

Adjacent sequences:  A124970 A124971 A124972 * A124974 A124975 A124976

KEYWORD

easy,nonn

AUTHOR

Franklin T. Adams-Watters, Nov 14 2006

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 16 21:37 EST 2019. Contains 319206 sequences. (Running on oeis4.)