proposition: Lemma Fib_rec n : natp n -> Fib (csucc (csucc n)) = Fib n +c Fib (csucc n).
proof: Proof. move => nN; rewrite /Fib/Fib2_rec (induction_terms _ _ (NS_succ nN)). by rewrite pr1_pair (induction_terms _ _ nN); aw. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(binomial div)