Section Properties1.
Context {K : AbsRing} {V : NormedModule K}.
(** Extensionality *)
(** Index offset *)

Lemma is_series_decr_n (a : nat -> V) (n : nat) (l : V) :
(0 < n)%nat -> is_series (fun k => a (n + k)%nat) (plus l (opp (sum_n a (pred n))))
-> is_series a l.