Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. A pentagonal pyramidal number is a figurate number that represents the number of objects in a pyramid with a pentagonal base. The nth pentagonal pyramidal number is equal to the sum of the first n pentagonal numbers. A figurate number is a number represented as a regular and discrete geometric pattern (e.g. dots) such as a polygonal number or a polyhedral number. The triangular numbers can be generalized in various ways. As used here, and in a number of other places, the term figurate number is meant to be broadly inclusive. In historical works about Greek mathematics the preferred term is figured number. For example A history of Greek Mathematics by T. Heath and Greek Mathematical Philosophy by E.A. Maziarz.