proposition: Lemma foo1 n: br n n = 'St(n.+1,n.+1).
proof: Proof. rewrite /br big_ord_recr /= binn 2!stir_nn big1 // => i _. by rewrite stir_small1 ?muln0. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype) mathcomp(ssrnat seq path div) mathcomp(fintype tuple finfun bigop finset binomial)