\begin{definition}[Definition:Centered Hexagonal Number/Sequence]
The sequence of centered hexagonal numbers, for $n \in \Z_{> 0}$, begins:
:$1, 7, 19, 37, 61, 91, 127, 169, 217, 271, 331, 397, 469, 547, 631, 721, 817, 919, \ldots$
{{OEIS|A003215}}
Category:Definitions/Centered Hexagonal Numbers
\end{definition}