OFFSET
1,1
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).
FORMULA
G.f.: B(x) - B(x)^2 + B(x^2) where B(x) is g.f. of A136794.
CROSSREFS
KEYWORD
nonn
AUTHOR
Christian G. Bower, Jan 21 2008
STATUS
approved