On some hypotheses concerning trees.
On some identities for the Fibonomial coefficients
On some inequalities for the skew Laplacian energy of digraphs.
On some influence of the weak subalgebra lattice on the subalgebra lattice.
On some Interconnections Between Combinatorial Optimization and Extremal Graph Theory
On some minimal problem
On some non-obvious connections between graphs and unary partial algebras
In the present paper we generalize a few algebraic concepts to graphs. Applying this graph language we solve some problems on subalgebra lattices of unary partial algebras. In this paper three such problems are solved, other will be solved in papers [Pió I], [Pió II], [Pió III], [Pió IV]. More precisely, in the present paper first another proof of the following algebraic result from [Bar1] is given: for two unary partial algebras and , their weak subalgebra lattices are isomorphic if and only...
On some partitions of a graph, I
On some partitions related to .
On some problem related to fundamental cycle sets of a graph: Research notes
On some problems in combinatorial set theory.
On some properties of the Laplacian matrix revealed by the RCM algorithm
In this paper we present some theoretical results about the irreducibility of the Laplacian matrix ordered by the Reverse Cuthill-McKee (RCM) algorithm. We consider undirected graphs with no loops consisting of some connected components. RCM is a well-known scheme for numbering the nodes of a network in such a way that the corresponding adjacency matrix has a narrow bandwidth. Inspired by some properties of the eigenvectors of a Laplacian matrix, we derive some properties based on row sums of a...
On some (pseudo) involutions in the Riordan group.
On some Ramsey and Turán-type numbers for paths and cycles.
On some regularities of graphs. I.
On some regularities of graphs. II.
On some symmetric designs with classical parameters.
On some systems of equations with constraints in a free group. – Addenda. (Sur certains systèmes d'équations avec constraintes dans un groupe libre. – Addenda.)
On some systems of equations with constraints in a free group. (Sur certains systèmes d'équations avec contraintes dans un groupe libre.)
On some variations of extremal graph problems
A set P of graphs is termed hereditary property if and only if it contains all subgraphs of any graph G belonging to P. A graph is said to be maximal with respect to a hereditary property P (shortly P-maximal) whenever it belongs to P and none of its proper supergraphs of the same order has the property P. A graph is P-extremal if it has a the maximum number of edges among all P-maximal graphs of given order. The number of its edges is denoted by ex(n, P). If the number of edges of a P-maximal...