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A136719 Number of labeled directed trees with n nodes. 0
1, 3, 27, 432, 10125, 314928, 12252303, 573308928, 31381059609, 1968300000000, 139234453205859, 10968475320188928, 952427511967417317, 90388408459919044608, 9308590679915771484375 (list; graph; refs; listen; history; internal format)
OFFSET

1,2

COMMENTS

A directed tree is a tree where each edge is assigned one or both directions.

REFERENCES

F. Bergeron, G. Labelle and P. Leroux, Combinatorial Species and Tree-Like Structures, Cambridge, 1998, pg 292 (4.1.58)

LINKS

Index entries for sequences related to trees

FORMULA

a(n) = A052756(n)/n.

CROSSREFS

Cf. A006965 (unlabeled version).

Sequence in context: A011781 A094577 A108525 * A159600 A159601 A193541

Adjacent sequences:  A136716 A136717 A136718 * A136720 A136721 A136722

KEYWORD

nonn

AUTHOR

Christian G. Bower (bowerc(AT)usa.net), Jan 18 2008

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Last modified February 14 16:57 EST 2012. Contains 205635 sequences.