Brieskorn_sphere
In mathematics, a Brieskorn manifold or Brieskorn–Phạm manifold, introduced by Egbert Brieskorn (1966, 1966b), is the intersection of a small sphere around the origin with the singular, complex hypersurface
studied by Frédéric Pham (1965).
Brieskorn manifolds give examples of exotic spheres.[1][2]