摘要
A proper total k-coloring of a graph G is a mapping from to such that no adjacent or incident elements in receive the same color. Let denote the sum of the colors on the edges incident with the vertex v and the color on v. A proper total k-coloring of G is called neighbor sum distinguishing if for each edge Let be the neighbor sum distinguishing total chromatic number of a graph G. PilA > niak and WoAniak conjectured that for any graph G, . In this paper, we show that if G is a graph with treewidth and , then . This upper bound confirms the conjecture for graphs with treewidth 3 and 4. Furthermore, when and , we show that and characterize graphs with equalities.