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A097627 Number of rooted directed trees on n nodes with a red root. 4
1, 2, 21, 280, 5465, 134556, 4051453, 143810416, 5884797969, 272701388980, 14116335883661, 807328717090248, 50554260752606377, 3440140092356781100, 252777268861251990045, 19946622760623381708256 (list; graph; refs; listen; history; internal format)
OFFSET

1,2

COMMENTS

Ditrees are well-colored directed trees. Well-colored means, each green vertex has at least a red child, each red vertex has no red child.

LINKS

C. Banderier, J.-M. Le Bars and V. Ravelomanana, Generating functions for kernels of digraphs

FORMULA

E.g.f.: A(x) = -C(-C(2x)/2), C(x) = e.g.f. of A000169.

CROSSREFS

Equals A052746(n) - A097628(n). Cf. A097629.

Sequence in context: A045726 A105712 A087677 * A094797 A196629 A196637

Adjacent sequences:  A097624 A097625 A097626 * A097628 A097629 A097630

KEYWORD

nonn

AUTHOR

Ralf Stephan, Aug 17 2004

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Last modified February 16 14:07 EST 2012. Contains 205930 sequences.