Hex Number
The Centered Hexagonal Number given by
where
is the 
th Triangular Number. The first few hex numbers are 1, 7, 19, 37, 61, 91, 127, 169, ...(Sloane's A003215). The Generating Function of the hex numbers is
The first Triangular hex numbers are 1 and 91, and the first few Square ones are 1,169, 32761, 6355441, ... (Sloane's A006051). Square hex numbers are obtained by solving theDiophantine Equation
The only hex number which is Square and Triangular is 1. There areno Cubic hex numbers.See also Magic Hexagon, Centered Square Number, Star Number, Talisman Hexagon
References
Conway, J. H. and Guy, R. K. The Book of Numbers. New York: Springer-Verlag, p. 41, 1996. Gardner, M. ``Hexes and Stars.'' Ch. 2 in Time Travel and Other Mathematical Bewilderments. New York: W. H. Freeman, 1988. Hindin, H. ``Stars, Hexes, Triangular Numbers, and Pythagorean Triples.'' J. Recr. Math. 16, 191-193, 1983-1984. Sloane, N. J. A. SequencesA003215/M4362and A006051/M5409in ``An On-Line Version of the Encyclopedia of Integer Sequences.''http://www.research.att.com/~njas/sequences/eisonline.html and Sloane, N. J. A. and Plouffe, S.The Encyclopedia of Integer Sequences. San Diego: Academic Press, 1995.
- Cosecant
- Coset
- Cosh
- Cosine
- Cosine Apodization Function
- Cosine Circle
- Cosine Integral
- Cosines Law
- Cosmic Figure
- Cosmological Theorem
- Costa-Hoffman-Meeks Minimal Surface
- Costa Minimal Surface
- Cosymmedian Triangles
- Cotangent
- Cotangent Bundle
- Cotes Circle Property
- Cotes Number
- Cotes' Spiral
- Coth
- Coulomb Wave Function
- Count
- Countable Additivity Probability Axiom
- Countable Set
- Countable Space
- Countably Infinite Set