Let $G$ be a group and $H$ a subgroup. Consider the ascending chain $$ H \leq N_G(H) \leq N_G(N_G H) \leq \cdots \leq N^{(k)}_G(H) \leq \cdots $$ of of iterated normalizers. Does: $$ H \trianglelefteq N_G(H) \trianglelefteq N_G(N_G H) \trianglelefteq \cdots \trianglelefteq N^{(k)}_G(H) \trianglelefteq \cdots. $$ Is there exist an example of $G$ and $H$ such thatwhere all the terms of the sequence are finite subgroups, but the chain fails to stabilize?