\input zb-basic
\input zb-ioport
\iteman{io-port 05996462}
\itemau{Kuba, Markus; Panholzer, Alois}
\itemti{Bilabelled increasing trees and hook-length formulae.}
\itemso{Eur. J. Comb. 33, No. 2, 248-258 (2012).}
\itemab
Summary: We introduce two different kinds of increasing bilabellings of trees, for which we provide enumeration formulae. One of the bilabelled tree families considered is enumerated by the reduced tangent numbers and is in bijection with a tree family introduced by {\it C. Poupard} [Eur. J. Comb. 10, No. 4, 369--374 (1989; Zbl 0692.05022)]. Both increasing bilabellings naturally lead to hook-length formulae for trees and forests; in particular, one construction gives a combinatorial interpretation of a formula for labelled unordered forests obtained recently by {\it W. Y. C. Chen}, {\it O. X. Q. Gao} and {\it P.I. Guo} [Electron. J. Comb. 16, No. 1, Research Paper R62, 16 p. (2009; Zbl 1180.05007)].
\itemrv{~}
\itemcc{}
\itemut{increasing bilabellings of trees}
\itemli{doi:10.1016/j.ejc.2011.09.043}
\end