Gauss circle problem

The Gauss circle problem is a classic problem in number theory and geometry that involves estimating the number of lattice points (points with integer coordinates) that lie within a circle of a certain radius centered at the origin in the Cartesian coordinate plane. More specifically, the problem asks how many integer points \((x, y)\) satisfy the inequality: \[ x^2 + y^2 \leq r^2 \] where \(r\) is the radius of the circle.