Given a triangle ABC (see figure above), the
circumcenter O, Nine-point center N, First F1 and Second F2 Fermat points
lie on a circle, called Lester circle.
This theorem was discovered by professor June A, Lester in 1996.
Reference: June A. Lester, "Triangles III: Complex triangle functions", Aequationes Mathematicae, volume 53, pages 4–35, 1997.