A136795 Number of unlabeled marked trees with n nodes.

2, 6, 20, 112, 662, 4596, 34032, 268280, 2201634, 18679362, 162611904, 1446148032, 13090979394, 120303384120, 1119971272340, 10544483234056, 100261309326082, 961692928106614, 9296529143261548, 90497666895840376

Offset: 1

Author

Christian G. Bower, Jan 21 2008

Keywords

• nonn

Comments

A marked tree is a tree where each node and edge is marked as + or -.

References

• F. Bergeron, G. Labelle and P. Leroux, Combinatorial Species and Tree-Like Structures, Cambridge, 1998, p. 293 (4.1.60).

Links

• Index entries for sequences related to trees

Crossrefs

Cf. A136794 (rooted tree version), A136797 (labeled version).

Formula

G.f.: B(x) - B(x)^2 + B(x^2) where B(x) is g.f. of A136794.