MathDB
Can the nominator of this sum be squarefree?

Source: Bulgarian Winter Tournament 2024 11.3

January 28, 2024
number theory

Problem Statement

Let q>3q>3 be a rational number, such that q24q^2-4 is a perfect square of a rational number. The sequence a0,a1,a_0, a_1, \ldots is defined by a0=2,a1=q,ai+1=qaiai1a_0=2, a_1=q, a_{i+1}=qa_i-a_{i-1} for all i1i \geq 1. Is it true that there exist a positive integer nn and nonzero integers b0,b1,,bnb_0, b_1, \ldots, b_n with sum zero, such that if i=0naibi=AB\sum_{i=0}^{n} a_ib_i=\frac{A} {B} for (A,B)=1(A, B)=1, then AA is squarefree?