The Double Roman Domination Numbers of Generalized Petersen Graphs P(n, 2).

A double Roman dominating function (DRDF) f on a given graph G is a mapping from V (G) to { 0 , 1 , 2 , 3 } in such a way that a vertex u for which f (u) = 0 has at least a neighbor labeled 3 or two neighbors both labeled 2 and a vertex u for which f (u) = 1 has at least a neighbor labeled 2 or 3. The weight of a DRDF f is the value w (f) = ∑ u ∈ V (G) f (u) . The minimum weight of a DRDF on a graph G is called the double Roman domination number γ d R (G) of G. In this paper, we determine the exact value of the double Roman domination number of the generalized Petersen graphs P (n , 2) by using a discharging approach. [ABSTRACT FROM AUTHOR]