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

Lemma exp3_step: forall e,
0 <= e < Int.max_signed ->
ff_exp (Int.repr 3) (Int.repr (1 + e)) = ff_mult (Int.repr 3) (ff_exp (Int.repr 3) (Int.repr e)).