proposition: Lemma dergSn n A : A^`(n.+1) = [~: A^`(n), A^`(n)].
proof: Proof. by []. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat fintype) mathcomp(bigop finset binomial fingroup morphism) mathcomp(automorphism quotient gfunctor)