# Problem 210: Obtuse Angled Triangles

![graphic](img210.gif)

Consider the set S(r) of points (x,y) with integer coordinates
satisfying |x| + |y| ≤ r. Let O be the point (0,0) and C the point
(r/4,r/4). Let N(r) be the number of points B in S(r), so that the
triangle OBC has an obtuse angle, i.e. the largest angle α satisfies 90°