Partitions of vertices
On désigne par le nombre de partitions de l’entier en parts supérieures ou égales à , et le nombre de partitions de de plus petite part . Dans un précédent article (voir [9]) un développement asymptotique de est obtenu uniformément pour ; on complète ce développement uniformément pour . Afin de prolonger les résultats jusqu’à , on donne un encadrement de valable pour en utilisant la relation où désigne le nombre de partitions de en exactement parts. On donne aussi une...
For a set S of connected graphs, a spanning subgraph F of a graph is called an S-factor if every component of F is isomorphic to a member of S. It was recently shown that every 2-connected cubic graph has a {Cₙ | n ≥ 4}-factor and a {Pₙ | n ≥ 6}-factor, where Cₙ and Pₙ denote the cycle and the path of order n, respectively (Kawarabayashi et al., J. Graph Theory, Vol. 39 (2002) 188-193). In this paper, we show that every connected cubic bipartite graph has a {Cₙ | n ≥ 6}-factor, and has a {Pₙ | n...
A path-neighborhood graph is a connected graph in which every neighborhood induces a path. In the main results the 3-sun-free path-neighborhood graphs are characterized. The 3-sun is obtained from a 6-cycle by adding three chords between the three pairs of vertices at distance 2. A Pk-graph is a path-neighborhood graph in which every neighborhood is a Pk, where Pk is the path on k vertices. The Pk-graphs are characterized for k ≤ 4.