Finite groups with many isolated subgroups

Abstract

Given a finite group $G$, we denote by $L(G)$ the subgroup lattice of $G$ and by $\mathrm{Isolated}(G)$ the set of isolated subgroups of $G$. In this note, we describe finite groups $G$ such that $|\mathrm{Isolated}(G)|=|L(G)|-k$, where $k=0,1,2$.