. Corollary Let be a finite action and let denote a transversal of the conjugacy classes of G. Then
Here is the faster version of the Cauchy-Frobenius Lemma.
Another formulation of the Cauchy-Frobenius Lemma makes use of the permutation representation defined by the action in question. (Actually in all our programs we apply this version of the Lemma.) The permutation group which is the image of under this representation, yields the action of on , which has the same orbits, and so we also have:
. Corollary
If denotes a finite -set, then (for
any group ) the following identity holds:
where
denotes a transversal of the conjugacy classes of .
Exercises
E . Let be finite and transitive. Consider an arbitrary and prove that