proposition: Lemma col1 n i : col i (1%:M : 'M_n) = delta_mx i 0.
proof: Proof. by apply/colP => j; rewrite !mxE eqxx andbT. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype finfun bigop finset fingroup perm order) mathcomp(div prime binomial ssralg countalg finalg zmodp)