On a question of K. Leeb
On A System Of All Maximal Chains (Antichains) Of A Graph
On an extension of Euler numbers and records of alternating permutations. (Sur une extension des nombres d'Euler et les records des permutations alternantes.)
On an identity for the cycle indices of rooted tree automorphism groups.
On an integer sequence related to a product of trigonometric functions, and its combinatorial relevance.
On an open problem of Green and Losonczy: exact enumeration of freely braided permutations.
On Arrangements of Jordan Arcs with Three Intersections per Pair.
On binary trees and Dyck paths
A bijection between the set of binary trees with n vertices and the set of Dyck paths of length 2n is obtained. Two constructions are given which enable to pass from a Dyck path to a binary tree and from a binary tree to a Dyck path.
On binary trees and permutations
Every binary tree is associated to a permutation with repetitions, which determines it uniquely. Two operations are introduced and used for the construction of the set of all binary trees. The set of all permutations which correspond to a given binary tree is determined and its cardinal number is evaluated.
On coefficients of circuit polynomials and characteristic polynomials.
On counting of periodic words. (Zur Abzählung periodischer Worte.)
On counting permutations by pairs of congruence classes of major index.
On descents in standard Young tableaux.
On Fibonacci-like sequences.
On general dissections of a polygon.
On general dissections of a polygon. (Short Communication).
On generalizations of the Stirling number triangles.
On generalized Dyck paths.
On generating functions involving the square root of a quadratic polynomial.
On generating series of coloured planar trees.