proposition: Lemma row1 n i : row i (1%:M : 'M_n) = delta_mx 0 i.
proof: Proof. by apply/rowP=> j; rewrite !mxE eq_sym. 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)