Definition:Pentagonal Pyramidal Number

Definition
Pentagonal pyramidal numbers are those denumerating a collection of objects which can be arranged in the form of a pentagonal pyramid.

The $n$th pentagonal pyramidal number $Q_n$ is defined as:
 * $\displaystyle P_n = \sum_{k \mathop = 1}^n P_k$

where $P_k$ is the $k$th pentagonal number.

Also see

 * Definition:Pyramidal Number
 * Definition:Tetrahedral Number
 * Definition:Square Pyramidal Number