Study of inverse sum indeg index

Abstract

Let $MG(i,n)$ $(1leq i leq 3)$ denote to the class of all $n$-vertex molecular graphs with minimum degree $ i$. The inverse sum indeg index of a graph is defined as $ISI=sum_{uvin E(G)} d_ud_v/(d_u+d_v)$, where $ d_{u}$ denotes to the degree of vertex $ u$. In this paper, we propose some extremal molecular graphs with the minimum and the maximum value of inverse sum indeg index in $MG(i,n)$.