1,2

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.

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

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

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

Sequence in context: A045726 A105712 A087677 this_sequence A094797 A099710 A098344

Adjacent sequences: A097624 A097625 A097626 this_sequence A097628 A097629 A097630

nonn

Ralf Stephan, Aug 17 2004