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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
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
KEYWORD
nonn,easy
AUTHOR
STATUS
approved

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Last modified April 14 14:52 EDT 2024. Contains 371665 sequences. (Running on oeis4.)