Bounds on Inverse Sum Indeg Index of Subdivision Graphs

Abstract

The inverse sum indeg index ISI(G) of a simple graph G is defined as the sum of the terms (d_G(u)d_G(v))/(d_G(u)+d_G(v)) over all edges uv of G, where d_G(u) denotes the degree of a vertex u of G. In this paper, we present several upper and lower bounds on the inverse sum indeg index of subdivision graphs and t-subdivision graphs. In addition, we obtain the upper bounds for inverse sum indeg index of S-sum, S_t-sum, S-product, S_t-product of graphs.