proposition: Lemma Vn_S : forall n, (0 < n)%nat -> Vn n = ln (Un (S n) / Un n).
proof: Proof. intros n Hn. unfold Vn. destruct n; [apply False_ind; lia|]. reflexivity. Qed.
imports: Reals Rsequence_facts Rseries_def Rseries_facts Rseries_usual Rpser Rintegral RTaylor Lia Lra Wallis