Degree sum of 3 independent vertices andZ3-connectivity

Fourth order and fourth sum connectivity indices of tetrathiafulvalene dendrimers

The m-order connectivity index (G) m of a graph G is     1 2 1 1 2 1 ... ... 1 ( ) i i im m v v v i i i m d d d  G where 1 2 1 ... i i im d d d  runs over all paths of length m in G and i d denotes the degree of vertex i v . Also,        1 2 1 1 2 1 ... ... 1 ( ) i i im m v v v i i i ms d d d X G is its m-sum connectivity index. A dendrimer is an artificially manufactured or synth...

Degree sum condition for Z3-connectivity in graphs

Let G be a 2-edge-connected simple graph on n vertices, let A denote an abelian group with the identity element 0, and let D be an orientation of G. The boundary of a function f : E(G) → A is the function ∂ f : V (G) → A given by ∂ f (v) = ∑ e∈E+(v) f (e) − ∑ e∈E−(v) f (e), where E(v) is the set of edges with tail v and E(v) is the set of edges with head v. A graph G is A-connected if for every...

On General Sum-Connectivity Index of Benzenoid Systems and Phenylenes

On the sum-connectivity index of unicyclic graphs with k pendent vertices

The sum-connectivity index R′(G) of a graph G is the sum of the weights (du +dv) − 2 of all edges uv of G, where du and dv are the degrees of the vertices u and v in G. This index was recently introduced in [B. Zhou, N. Trinajstić, On a novel connectivity index, J. Math. Chem. 46(2009), 1252–1270]. In this paper, we give the sharp lower bound of the sum-connectivity index of n-vertex unicyclic ...

Cycle Lengths in Hamiltonian Graphs with a Pair of Vertices Having Large Degree Sum

Agraph of order n is said to be pancyclic if it contains cycles of all lengths from three to n. Let G be a Hamiltonian graph and let x and y be vertices of G that are consecutive on some Hamiltonian cycle in G. Hakimi and Schmeichel showed (J Combin Theory Ser B 45:99–107, 1988) that if d(x) + d(y) ≥ n then either G is pancyclic, G has cycles of all lengths except n − 1 or G is isomorphic to a ...