proposition: Lemma block_mxEul i j : A (lshift m2 i) (lshift n2 j) = Aul i j.
proof: Proof. by rewrite col_mxEu row_mxEl. 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)