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Published online by Cambridge University Press: 27 January 2022
If G is permutation group acting on a finite set
$\Omega $
, then this action induces a natural action of G on the power set
$\mathscr{P}(\Omega )$
. The number
$s(G)$
of orbits in this action is an important parameter that has been used in bounding numbers of conjugacy classes in finite groups. In this context,
$\inf ({\log _2 s(G)}/{\log _2 |G|})$
plays a role, but the precise value of this constant was unknown. We determine it where G runs over all permutation groups not containing any
${{\textrm {A}}}_l, l> 4$
, as a composition factor.
This research was supported by NSF-REU grant DMS-1757233 and NSA grant H98230-21-1-0333. Y. Yang was also partially supported by a grant from the Simons Foundation (#499532).