On the Number of All Substructures Containing at Most Four Edges

Abstract

Let G be a simple graph with order n , n ≥ 5, and adjacency matrix A ( G ). In this paper, we determine the number of all substructures having at most four edges in terms of its adjacency matrix A ( G ) together with some graph invariants determined by A ( G ). Then, as applications, we provide an algebraic expression for the second Zagreb index and || A 4 || of a graph.