# n’th Pentagonal Number in C++

C++Server Side ProgrammingProgramming

In this tutorial, we are going to write a program that finds the n-th pentagonal number.

A pentagonal number is a number represented as dots or pebbles arranged in the shape of a regular polygon. Refer to the wiki for better understanding.

The n-th pentagonal number is (3 * n * n - n) / 2

## Example

Let's see the code.

Live Demo

#include<bits/stdc++.h>
using namespace std;
int getNthPentagonalNumber(int n) {
return (3 * n * n - n) / 2;
}
int main() {
int n = 7;
cout << getNthPentagonalNumber(n) << endl;
return 0;
}

## Output

If you run the above code, then you will get the following result.

70
Published on 29-Jun-2021 09:42:20