simple induction m; auto with arith.
intros.
simpl in |- *.
elim H.
elim exp_n_plus_mult; auto with arith.
Qed.
Hint Resolve exp_n_permut.

Lemma exp_n_plus_p1 : forall n p : nat, exp_n n (p + 1) = n * exp_n n p.
simple induction p; simpl in |- *.