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


Let's see the code.

 Live Demo

using namespace std;
int getNthPentagonalNumber(int n) {
   return (3 * n * n - n) / 2;
int main() {
   int n = 7;
   cout << getNthPentagonalNumber(n) << endl;
   return 0;


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

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