The annihilation number does not bound the 2-domination number from the above

Jun Yue, Shizhen Zhang, Yiping Zhu +2

The $2$-domination number ${\gamma }_2(G)$ of a graph $G$ is the minimum cardinality of a set $S\subseteq V(G)$ such that every vertex from $V(G)\setminus S$ is adjacent to at least two ve…