proposition: Lemma nbder_gt0 n: 0 < nder n.+2.
proof: Proof. by elim:n => // n ha; rewrite nderS muln_gt0 addn_gt0 ha. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype) mathcomp(ssrnat seq path div) mathcomp(fintype tuple finfun bigop finset binomial)