\begin{definition}[Definition:Heptagonal Pyramidal Number]
'''Heptagonal pyramidal numbers''' are those denumerating a collection of objects which can be arranged in the form of a heptagonal pyramid.
The $n$th '''heptagonal pyramidal number''' $Q_n$ is defined as:
:$\ds Q_n = \sum_{k \mathop = 1}^n H_k$
where $H_k$ is the $k$th heptagonal number.
\end{definition}