proposition: Lemma fib_smonotone_bis a b: a < b -> fib a.+2 < fib b.+2.
proof: Proof. by move => h; apply:fib_smonotone; rewrite !ltnS h. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(seq path fintype div bigop binomial) mathcomp(prime finset ssralg ssrnum ssrint)