(** * Unicity *)

Lemma Bessel1_uniqueness (a : nat -> R) (n : nat) :
(Rbar_lt 0 (CV_radius a)) ->
(forall x : R, x^2 * Derive_n (PSeries a) 2 x + x * Derive (PSeries a) x + (x^2 - (INR n)^2) * PSeries a x = 0)
-> {b : R | forall x, PSeries a x = b * Bessel1 n x}.