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Article
On the Irregularity of \(\pi \) -Permutation Graphs, Fibonacci Cubes, and Trees
The irregularity of a graph G is the sum of \(|\mathrm{deg}(u) - \mathrm{deg}(v)|\) | deg ( u ) - deg ( v ) | over all edges uv of G. In this paper, this invariant is considered on \(\pi \) π -permutatio...
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Article
M-polynomial revisited: Bethe cacti and an extension of Gutman’s approach
The M-polynomial of a graph G is defined as \(\sum _{i\le j} m_{i,j}(G)x^iy^j\) ...
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Article
Adjacent q-Cycles in Permutations
We introduce a new permutation statistic, namely, the number of cycles of length q consisting of consecutive integers, and consider the distribution of this statistic among the permutations of {1, 2, . . . , n}. ...
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Article
Restricted Simsun Permutations
A permutation is simsun if for all k, the subword of the one-line notation consisting of the k smallest entries does not have three consecutive decreasing elements. Simsun permutations were introduced by Simion a...
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Article
Production Matrices and Riordan Arrays
We translate the concept of succession rule and the ECO method into matrix notation, introducing the concept of production matrix. This allows us to combine our method with other enumeration techniques using matr...
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Article
A Simple and Unusual Bijection for Dyck Paths and its Consequences
In this paper we introduce a new bijection from the set of Dyck paths to itself. This bijection has the property that it maps statistics that appeared recently in the study of patternavoiding permutations into...
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Chapter and Conference Paper
New Statistics on Non-crossing Trees
A non-crossing tree is a tree drawn on the plane having as vertices a set of points on the boundary of a circle, and whose edges are straight line segments and do not cross. Continuing previous research on non...
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Article
On the centre of flexure
Dans une publication publiée en 1950,Berman a déterminé les coordonnées du centre de flexion d'une barre prismatique lorsqu'on connaît seulement les valeurs de la fonction de torsion sur le contour.