proposition: Lemma double_le3 n: n.+1 < (n.+1).*2.
proof: Proof. by rewrite doubleS !ltnS double_le1. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(seq path fintype div bigop binomial) mathcomp(prime finset ssralg ssrnum ssrint)