(* works, but very slow! Lemma exp_table_correct : forall a : nat, (a < 256)%nat -> nth a ff_exp_table Int.zero = exp3 a. *)

Lemma nth_cons_S: forall {T: Type} (n: nat) (h: T) (tl: list T),
nth (S n) (h :: tl) = nth n tl.