3 papers
math.CO2020
Crossings and nestings over some Motzkin objects and -Motzkin numbers
Sandrataniaina R. Andriantsoa, Paul M. Rakotomamonjy
We examine the enumeration of certain Motzkin objects according to the numbers of crossings and nestings. With respect to continued fractions, we compute and express the distributi…
math.CO2019
Crossings over permutations avoiding some pairs of patterns of length three
Paul M. Rakotomamonjy, Sandrataniaina R. Andriantsoa, Arthur Randrianarivony
In this paper, we compute the distributions of the statistic number of crossings over permutations avoiding one of the pairs , and . The obt…
math.CO2019
New combinatorial interpretations of the binomial coefficients
Paul M. Rakotomamonjy, Sandrataniaina R. Andriantsoa
Using generating functions and some trivial bijections, we show in this paper that the binomial coefficients count the set of (123,132) and (123,213)-avoiding permutations accordin…