The IC-indices of Some Complete Multipartite Graphs

Abstract

A coloring of a connected graph $G$ is a function $f$ mapping the vertex set of $G$ into the set of all integers. For any subgraph $H$ of $G$, we denote the sum of the values of $f$ on the vertices of $H$ as $f(H)$. If for any integer $k\in \{1,2,\cdots,f(G)\}$, there exists an induced connected subgraph $H$ of $G$ such that $f(H) = k$, then the coloring $f$ is called an IC-coloring of $G$. The IC-index of $G$, denoted as $M(G)$, is the maximum value of $f(G)$ over all possible IC-colorings $f$ of $G$. In this paper, we present a useful method from which a lower bound on the IC-index of any complete multipartite graph can be derived. Subsequently, we show that, for $m\geq 2 ~\mbox{and} ~n\geq 2$, our lower bound on $M(K_{1(n),m})$ is the exact value of it.