“…However, for the sum n x λ 2 f (n 3 ), the condition (C) in Lemma 2.1 is not satisfied, and for the sum n x λ 2 f (n 4 ), the corresponding generating function has a factor L(sym 6 f ×sym 6 f, s), whose analytic properties are not clear (since the automorphy of the jth symmetric power lift of an automorphic cuspidal representation over GL 2 (A Q ) is only known for j ≤ 4, see e.g. [3,7,8,22]). …”