This result is best possible for k = 3 since the Petersen graph is a nonhamiltonian, 2-connected, 3-regular graph on 10 vertices. It is essentially best possible for k > 4 since there exist non-hamiltonian, 2-connected, kregular graphs on 3k + 4 vertices for k even, and 3k + 5 vertices for all k. Examples of such graphs are given in [ 1, 3 1. The problem of determining the values of k for which...

a fullerene graph is a 3−connected planar graph whose faces are pentagons and hexagons.the clar number of a fullerene is the maximum size of sextet patterns, the sets of disjointhexagons which are all m-alternating for a kekulé structure m of f. an exact formula of clarnumber of some fullerene graphs and a class of carbon nanocones are obtained in this paper.

We focus on the algorithm underlying the main result of [6]. This is an algebraic formula to generate all connected graphs in a recursive and efficient manner. The key feature is that each graph carries a scalar factor given by the inverse of the order of its group of automorphisms. In the present paper, we revise that algorithm on the level of graphs. Moreover, we extend the result subsequentl...

The problem on the Hamiltonicity of graphs is well studied in discrete algorithm and graph theory, because of its relation to traveling salesman problem (TSP). Starting with Tutte’s result, stating that every 4-connected planar graph is Hamiltonian, several researchers have studied the Hamiltonicity of graphs on surfaces. Extending Tutte’s technique, Thomassen proved that every 4-connected plan...

The classical Steiner tree problem in weighted graphs seeks a minimum weight connected subgraph containing a given subset of the vertices (terminals). We present a new polynomialtime heuristic that achieves a best-known approximation ratio of 1 + ln 3 2 ≈ 1.55 for general graphs, and best-known approximation ratios of ≈ 1.28 for quasi-bipartite graphs (i.e., where no two non-terminals are adjac...

In 1962, S. L. Hakimi proved necessary and sufficient conditions for a given sequence of positive integers d1, d2, . . . , dn to be the degree sequence of a non–separable graph or that of a connected graph. Our goal in this note is to utilize these results to prove closed formulas for the functions dns(2m) and dc(2m), the number of degree sequences with degree sum 2m representable by non–separa...

We continue our investigation of graphsG for which the least eigenvalue λ(G) is minimal among the connected graphs of prescribed order and size. We provide structural details of the bipartite graphs that arise, and study the behaviour of λ(G) as the size increases while the order remains constant. The non-bipartite graphs that arise were investigated in a previous paper [F.K. Bell, D. Cvetković...

Let G be a connected graph with minimum degree id="M3"> δ and vertex-connectivity id="M4"> κ . The id="M5"> is id="M6"> k -connected if id="M7"> ≥ , maximally id="M8"> = super-connected every vertex-cut isol...

For graphs G and H, an H-coloring of G is a map from the vertices of G to the vertices of H that preserves edge adjacency. We consider the following extremal enumerative question: for a given H, which connected n-vertex graph with minimum degree δ maximizes the number of H-colorings? We show that for non-regular H and sufficiently large n, the complete bipartite graph Kδ,n−δ is the unique maxim...