proposition: Lemma integer_induction (s:fterm) a: exists! f, [/\ source f = Nat, surjection f, Vf f \0c = a & forall n, natp n -> Vf f (csucc n) = s (Vf f n)].
proof: Proof. move: (integer_induction0 (fun _ x:Set => s x) a) => //. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(binomial div)