Given equally spaced points on a circle, we define an -star polygon as an -gon having those points as vertices. Two -star polygons differing by a rotation/reflection are considered different.
For example, there are twelve -star polygons shown below.
For an -star polygon , let be the number of its self intersection points.Let be the sum of over all -star polygons .For the example above because in total there are self intersection points.
Some star polygons may have intersection points made from more than two lines. These are only counted once. For example, , shown below is one of the sixty -star polygons. This one has .