For a nontrivial graph G, its first and second Zagreb coindices are defined as the sum of degree sum of of nonadjacent vertex pairs and the sum of degree product of nonadjacent vertices pairs, respectively. Motivated by the work in [1], we study Zagreb coindices of a new kind of composite graph, namely, double graph. For any given nontrivial graph, explicit formulas are given for the Zagreb coindices of its doubl...
