A Figurate Number in which layers of Polygons are drawn centered about a point instead of with the point at a Vertex.
See also Centered Pentagonal Number, Centered Square Number, Centered Triangular Number
Sloane, N. J. A. Sequence
in ``An On-Line Version of the Encyclopedia of Integer Sequences.''
http://www.research.att.com/~njas/sequences/eisonline.html and extended entry in
Sloane, N. J. A. and Plouffe, S.
The Encyclopedia of Integer Sequences. San Diego: Academic Press, 1995.