Antoine's Horned Sphere
A topological 2-sphere in 3-space whose exterior is not Simply Connected. The outer complement of Antoine'shorned sphere is not Simply Connected. Furthermore, the group of the outer complement is not even finitelygenerated. Antoine's horned sphere is inequivalent to Alexander's Horned Sphere since the complement in 
of the bad points for Alexander's Horned Sphere is Simply Connected.
References
Alexander, J. W. ``An Example of a Simply-Connected Surface Bounding a Region which is not Simply-Connected.'' Proc. Nat. Acad. Sci. 10, 8-10, 1924. Rolfsen, D. Knots and Links. Wilmington, DE: Publish or Perish Press, pp. 76-79, 1976.
- Integral Equation
- Integral of Motion
- Integral Sign
- Integral Test
- Integral Transform
- Integrand
- Integrating Factor
- Integration
- Integration by Parts
- Integration Lattice
- Intension
- Interchange Graph
- Interest
- Interior
- Interior Angle Bisector
- Intermediate Value Theorem
- Internal Bisectors Problem
- Internal Knot
- Interpolation
- Interquartile Range
- Interradius
- Intersection
- Interspersion
- Intersphere
- Interval