Published online by Cambridge University Press: 01 August 2018
For a finite group $G$, denote by
$\unicode[STIX]{x1D707}(G)$ the degree of a minimal permutation representation of
$G$. We call
$G$ exceptional if there is a normal subgroup
$N\unlhd G$ with
$\unicode[STIX]{x1D707}(G/N)>\unicode[STIX]{x1D707}(G)$. To complete the work of Easdown and Praeger [‘On minimal
faithful permutation representations of finite groups’, Bull. Aust.
Math. Soc.38(2) (1988), 207–220], for all primes
$p\geq 3$, we describe an exceptional group of order
$p^{5}$ and prove that no exceptional group of order
$p^{4}$ exists.