Abstract:
It is proved that if $G$ is a group without elements of order $2$, and the normal closure of every $2$-generated subgroup of $G$ is a nilpotent group of class at most $3$, then $G$ will be a nilpotent group of class at most $4$. It is also shown that the restriction on second-order elements cannot be lifted.
Keywords:nilpotent group, normal closure of subgroup, Levi class, variety, quasivariety.