proposition: Lemma mcoeffC (c : G) k : c%:MP@_k = c *+ (k == 1%M :> K).
proof: Proof. by rewrite mcoeffU eq_sym. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(seq path choice finset fintype finfun) mathcomp(tuple bigop ssralg ssrint ssrnum) xfinmap