Question 62
Find every integer $k$ that satisfies the following condition.
There are infinitely many triplet $(a, b, c)$ of integers such that $(a^2 - k)(b^2 - k) = c^2 - k$.
There are infinitely many triplet $(a, b, c)$ of integers such that $(a^2 - k)(b^2 - k) = c^2 - k$.