We show that there are \( \ll N^{2/3+o(1)}\) squares in any given arithmetic progression of length \( N\). This was later improved by Bombieri and Zannier to \( \ll N^{3/5+o(1)}\); while the conjecture is that the maximum is \( \sqrt{8N/3}+O(1) \), given by
\( 1, 25, 49,\ldots, 24N-23\).
Article