# Octacontagon Number

Given a number N, the task is to find Nth Octacontagon number.

A Octacontagon numberr is class of figurate number. It has 80 – sided polygon called octacontagon. The N-th octacontagon number count’s the 80 number of dots and all others dots are surrounding with a common sharing corner and make a pattern. The first few octacontagonol numbers are 1, 80, 237, 472 …

Examples:

Input: N = 2
Output: 80
Explanation:
The second octacontagonol number is 80.

Input: N = 3
Output: 237

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Approach: The N-th octacontagon number is given by the formula:

• Nth term of s sided polygon = • Therefore Nth term of 80 sided polygon is Below is the implementation of the above approach:

## C++

 // C++ program for above approach  #include  using namespace std;     // Finding the nth octacontagon Number  int octacontagonNum(int n)  {      return (78 * n * n - 76 * n) / 2;  }     // Driver Code  int main()  {      int n = 3;      cout <<"3rd octacontagon Number is = "          << octacontagonNum(n);         return 0;  }     // This code is contributed by shivanisinghss2110

## C

 // C program for above approach  #include  #include     // Finding the nth octacontagon Number  int octacontagonNum(int n)  {      return (78 * n * n - 76 * n) / 2;  }     // Driver program to test above function  int main()  {      int n = 3;      printf("3rd octacontagon Number is = %d",             octacontagonNum(n));         return 0;  }

## Java

 // Java program for above approach  import java.util.*;  class GFG{     // Finding the nth octacontagon Number  static int octacontagonNum(int n)  {      return (78 * n * n - 76 * n) / 2;  }     // Driver Code  public static void main(String args[])  {      int n = 3;      System.out.print("3rd octacontagon Number is = " +                                    octacontagonNum(n));  }  }     // This code is contributed by Akanksha_Rai

## Python3

 # Python3 program for above approach      # Finding the nth octacontagon number   def octacontagonNum(n):          return (78 * n * n - 76 * n) // 2    # Driver code  n = 3 print("3rd octacontagon Number is = ",                      octacontagonNum(n))      # This code is contributed by divyamohan123

## C#

 // C# program for above approach  using System;  class GFG{     // Finding the nth octacontagon Number  static int octacontagonNum(int n)  {      return (78 * n * n - 76 * n) / 2;  }     // Driver Code  public static void Main()  {      int n = 3;      Console.Write("3rd octacontagon Number is = " +                                 octacontagonNum(n));  }  }     // This code is contributed by Akanksha_Rai

Output:

3rd octacontagon Number is = 237


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