Question 167
a) Find at least one positive integer $n$, which can be represented both as $n = a^2 - b$ and $n = c^2 - d$, where $a, b, c, d$ are divisors of $n$ and $a \neq c$.
b) Prove that there exist infinitely many positive integers $n$ satisfying a).
b) Prove that there exist infinitely many positive integers $n$ satisfying a).