Since, by (2.1), |yj | ≤ √2 + |ν|, we find that |sn| ≤ (
√2 + |ν|)L(P).
In the remainder of this section we shall prove that the sequence
s1, s2, s3,... defined in (2.2) is not ultimately periodic, unless α is an algebraic
integer whose conjugates over Q(i) all lie in the unit disc |z| ≤ 1 and
ξ ∈ Q(α, i).