Forgotten reduced neighborhood topological index

Topological graph indices are the most important applications of graph theory. In the last few decades, such applications have been increasingly in use for mathematicians, chemists, pharmacologists. Due to these applications, a large number of these indices are defined and used in several areas. The first and second reduced neighborhood Zagreb indices have been recently defined by [Formula: see text] In this paper, following the recent study of reduced neighborhood Zagreb indices, we introduced the forgotten reduced neighborhood topological index, obtained values of some families of graphs and also computed the exact values of this index for graphene and honeycomb networks.