Centered Pentagonal Number
A Centered Polygonal Number consisting of a central dot with five dots around it, and then additional dots in thegaps between adjacent dots. The general term is 
, and the first few such numbers are 1, 6, 16, 31, 51, 76,... (Sloane's A005891). The Generating Function of the centered pentagonal numbers is
See also Centered Square Number, Centered Triangular Number
References
Sloane, N. J. A. SequenceA005891/M4112in ``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.
- Hexad
- Hexadecagon
- Hexadecimal
- Hexaflexagon
- Hexagon
- Hexagonal Number
- Hexagonal Pyramidal Number
- Hexagonal Scalenohedron
- Hexagonal Tiling
- Hexagon Polyiamond
- Hexagram
- Hexagrammum Mysticum Theorem
- Hexahedron
- Hexahemioctahedron
- Hexakaidecagon
- Hexakis Icosahedron
- Hexakis Octahedron
- Hex Game
- Hexlet
- HexLife
- Hex Number
- Hexomino
- Hex (Polyhex)
- Hex Pyramidal Number
- Heyting Algebra