Admitted. (* (*N*) QuickChick beq_id_true. *)

(* Specifications: *)
(* Leo: Theorem nth_error_after_last: forall (n : nat) (X : Type) (l : list X), *)
Theorem nth_error_after_last: forall  (X : Type) (l : list X) (n : nat),
length l = n ->
nth_error l n = None.