A centered pentagonal number is a centered polygonal number consisting of a central dot surrounded by concentricpentagons,
where
is a nonnegative integer and the th pentagon contains dots for .
The general term for ,
1, 2, ... is , and the first few such numbers are 1,
6, 16, 31, 51, 76, ... (OEIS A005891). The
generating function of the centered pentagonal
numbers, convergent for ,
is
concentric pentagons,
where 
is a nonnegative integer and the 
th pentagon contains 
dots for 
.
The general term for 
,
1, 2, ... is 
, and the first few such numbers are 1,
6, 16, 31, 51, 76, ... (OEIS A005891). The
generating function of the centered pentagonal
numbers, convergent for 
,
is
