proposition: Lemma odd_cycle_type s : odd_perm s = odd (sumn (cycle_type s) - size (cycle_type s)).
proof: Proof. have:= size_part (intpartnP (cycle_type s)). rewrite sumn_intpartn size_cycle_type => lept. by rewrite oddB. Qed.
imports: mathcomp.ssreflect.ssreflect mathcomp(ssrfun ssrbool eqtype ssrnat seq choice fintype) mathcomp(tuple finfun finset path bigop) mathcomp(fingroup perm action) mathcomp(ssralg matrix mxalgebra algC classfun) partition tools sorted permcomp fibered_set cycles