cut (forall (m : nat) a, sizel3 a < m -> Acc lessP3 a).
intros H' a.
apply H' with (m := S (sizel3 a)); auto.
intros m; elim m; clear m.
intros a H; inversion H.
intros p H' a H'0; apply Acc_intro.
intros y H'1; apply H'.
unfold lessP in H'1; apply lt_le_trans with (sizel3 a); auto with arith.
Qed.
Hint Resolve wf_lessP3.
Set Implicit Arguments.
Unset Strict Implicit.
Definition eqPf :
forall pq, {eqP (fst pq) (snd pq)} + {~ eqP (fst pq) (snd pq)}.
intros pq; pattern pq in |- *;
apply well_founded_induction with (R := lessP) (1 := wf_lessP);
clear pq.
intros pq; case pq; simpl in |- *; clear pq.
intros p; case p; clear p.
intros q; case q; clear q.
intros H'; left; constructor.
intros b q H'; right; red in |- *; intros H'0; inversion H'0.
intros a p q; case q; clear q.
intros H'; right; red in |- *; intros H'0; inversion H'0.
intros b q Rec; case (eqTerm_dec _ _ eqA_dec n a b); simpl in Rec;
intros eqTerm0.
case (Rec (p, q)); unfold lessP in |- *; simpl in |- *; auto with arith.
intros H'; left; auto.
change (eqP (pX a p) (pX b q)) in |- *; auto.
intros H'; right; red in |- *; intros H'0.
apply H'.
apply eqp_inv3r with (a := a) (b := b); auto.
right; red in |- *; intros H'.
apply eqTerm0.
apply eqp_eqTerm with (p := p) (q := q); auto.
Defined.
Definition seqP : poly A0 eqA ltM -> poly A0 eqA ltM -> Prop.
intros sp1 sp2; case sp1; case sp2.
intros p1 H'1 p2 H'2; exact (eqP p1 p2).
Defined.
Set Strict Implicit.
Unset Implicit Arguments.

Theorem seqp_dec : forall p q : poly A0 eqA ltM, {seqP p q} + {~ seqP p q}.
intros p q; case p; case q; simpl in |- *.