This document discusses pentagonal numbers, which are numbers that can be represented as a pentagonal pattern of dots. It provides a general formula for calculating pentagonal numbers and cites two websites as sources for more information on pentagonal numbers, including their definitions and properties.

1. Pentagonal Numbers
Ion Andreea-Elena
Clasa a VI-a D

2. Introduction
 A pentagonal number is a number that
can be shown as a pentagonal pattern
of dots.

4. General formula

5. Examples

6. Sources
 http://www.math-magic.com/misc/pentagonal.htm
 https://www.mathsisfun.com/definitions/pentagonal-number.html

7. Sources
 http://www.math-magic.com/misc/pentagonal.htm
 https://www.mathsisfun.com/definitions/pentagonal-number.html