proposition: Lemma mesym1_setT : mesym1 setT = (\sum_(i < n) U_(i))%MM.
proof: Proof. apply/mnmP=> i; rewrite mnmE mnm_sumE in_setT /=. rewrite (bigD1 i) //= mnmE eqxx big1 ?addn0 //. by move=> j; rewrite mnmE => /negbTE->. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq path) mathcomp(choice fintype tuple finfun bigop finset binomial) mathcomp(order fingroup perm ssralg zmodp poly ssrint) mathcomp(matrix vector) mathcomp(bigenough) ssrcomplements freeg