👉 A pentagonal number is a figurate number that extends the concept of triangular numbers to other shapes. A pentagonal number is a number that can be represented as 5n + 1, where n is any integer. Pentagonal numbers are important in geometry and mathematics because they serve as a representation of certain geometric figures. Here's how you can define a pentagonal number: Pentagonal Number Formula: For any positive integer n: \[ P_n = \frac{n(n+1
