intros.
intro i.
simpl in |- *.
induction n.
auto with algebra.
case i.
auto with algebra.
Qed.

Lemma cons_const_seq :
forall (n : Nat) (a a' a'' : A),
a =' a' in _ ->
a' =' a'' in _ -> a;; const_seq n a' =' const_seq (S n) a'' in _.