revert i j; induction v; intros i j Hi.
+ cbn; intros ? % divides_1_inv % not_qs_1; auto.
+ cbn; intros [ H % divides_pow | H  ] % divides_mult_inv; eauto.
* eapply primestream_divides in H; omega.
* eapply IHv in H; eauto.
Qed.

Lemma exp_inv_inc n u v1 :
@exp n 0 (vec_change v1 u (S (vec_pos v1 u))) = qs u * exp 0 v1.