Question 141
How many equilateral hexagons of side length $\sqrt{13}$ have one vertex at $(0,0)$ and the other five vertices at lattice points?
(A lattice point is a point whose Cartesian coordinates are both integers. A hexagon may be concave but not self-intersecting.)
(A lattice point is a point whose Cartesian coordinates are both integers. A hexagon may be concave but not self-intersecting.)