F-Index of Four Operations on Graphs

The F-index of a graph is defined as the sum of cubes of the vertex degrees of the graph which was introduced in 1972, in the same paper where the first and second Zagreb indices were introduced. In this paper we study the F-index of four operations on graphs which were introduced by Eliasi and Taeri [M. Eliasi, B. Taeri, Four new sums of graphs and their Wiener indices, $\mathit{\text{Discrete}}\mathit{\text{Appl.}}\mathit{\text{Math.}}$$\mathbf{\text{157}}$(2009) 794–803.].