Entringer numbers and Poupard Calculus

Speaker: Dominique Foata
Date: 13/11/2013
Time: 14:00 - 15:30

Location: RISC Seminar room pond

Refinements of the celebrated tangent and secant numbers give rise to bivariate statistical distributions that can be expressed, either by a finite difference equation system, or by a three-variate exponential generating function. The underlying combinatorial sets, counted by tangent and secant numbers, are the alternating permutations, or the André permutations of the two kinds, or still the binary increasing trees. Emphasis will be made on the calculation of the involved series.