On the bounds of forgotten topological index.

Abstract

The forgotten topological index is defined as the sum of cubes of the degrees of the vertices of the molecular graph G. In this paper, we obtain, analyze and compare various lower bounds for the forgotten topological index involving the number of vertices, edges, maximum and minimum vertex degree. Next, we give Nordhaus-Gaddum-type inequalities for the forgotten topological index and coindex. Finally, we correct the number of extremal chemical trees on 15 vertices.