proposition: Lemma leib_corner n : \lcm_(i < n.+1) 'L(i, 0) = \lcm_(i < n.+1) 'L(n, i).
proof: Proof. elim: n => [|n IH]; first by rewrite !big_ord_recr !big_ord0 /=. rewrite big_ord_recr /= IH lcmnC. rewrite (eq_bigr (fun i : 'I_n.+1 => 'L(n, 0 + i))) //. by rewrite leib_line. Qed.
imports: mathcomp(all_ssreflect)