Question 78
Find all pairs $(b, c)$ of positive integers such that the sequence defined by $a_1 = b$, $a_2 = c$ and
$$
a_{n+2} = |4a_{n+1} - 3a_n|, \forall n \ge 1
$$
has only a finite number of composite terms.
$$
a_{n+2} = |4a_{n+1} - 3a_n|, \forall n \ge 1
$$
has only a finite number of composite terms.