A Centered Polygonal Number consisting of a central dot with five dots around it, and then additional dots in the
gaps 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

**References**

Sloane, N. J. A. Sequence
A005891/M4112
in ``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.

© 1996-9

1999-05-26