data/problems/210.yml
---
:id: 210
:name: Obtuse Angled Triangles
:url: https://projecteuler.net/problem=210
:content: "\r Consider the set S(r) of points (x,y) with integer coordinates satisfying
|x| + |y| ≤ r. \nLet O be the point (0,0) and C the point (r/4,r/4). \nLet 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°\\<α\\<180°. \nSo, for example, N(4)=24 and
N(8)=100.\n\nWhat is N(1,000,000,000)?\n\n"