Heptagonal number

Given a number n, the task is to find Nth heptagonal number. A Heptagonal number represents heptagon and belongs to a figurative number. Heptagonal has seven angles, seven vertices, and seven-sided polygon.

Examples :

Input : 2
Output :7



Input :15
Output :540

Heptagonal

Few Heptagonal numbers are :
1, 7, 18, 34, 55, 81, 112, 148, 189, 235………..

A formula to calculate Nth Heptagonal number:

  \begin{math}  Hep_{n}=((5*n*n)-3*n)/2 \end{math}  

C++

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// C++ program to find the
// nth Heptagonal number
#include <iostream>
using namespace std;
  
// Function to return Nth Heptagonal
// number
int heptagonalNumber(int n)
{
    return ((5 * n * n) - (3 * n)) / 2;
}
  
// Drivers Code
int main()
{
  
    int n = 2;
    cout << heptagonalNumber(n) << endl;
    n = 15;
    cout << heptagonalNumber(n) << endl;
  
    return 0;
}

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Java

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// Java program to find the
// nth Heptagonal number
import java.io.*;
  
class GFG 
{
// Function to return 
// Nth Heptagonal number
static int heptagonalNumber(int n)
{
    return ((5 * n * n) - (3 * n)) / 2;
}
  
// Driver Code
public static void main (String[] args) 
{
    int n = 2;
    System.out.println(heptagonalNumber(n));
    n = 15;
    System.out.println(heptagonalNumber(n));
}
}
  
// This code is contributed by anuj_67.

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Python3

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# Program to find nth 
# Heptagonal number
  
# Function to find 
# nth Heptagonal number
def heptagonalNumber(n) :
      
    # Formula to calculate 
    # nth Heptagonal number
    return ((5 * n * n) - 
            (3 * n)) // 2
  
# Driver Code
if __name__ == '__main__' :
    n = 2
    print(heptagonalNumber(n))
    n = 15
    print(heptagonalNumber(n))
                  
# This code is contributed
# by ajit

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C#

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// C# program to find the
// nth Heptagonal number
using System;
  
class GFG 
{
// Function to return 
// Nth Heptagonal number
static int heptagonalNumber(int n)
{
    return ((5 * n * n) - 
            (3 * n)) / 2;
}
  
// Driver Code
public static void Main () 
{
    int n = 2;
    Console.WriteLine(heptagonalNumber(n));
    n = 15;
    Console.WriteLine(heptagonalNumber(n));
}
}
  
// This code is contributed by anuj_67.

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PHP

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<?php
// PHP program to find the
// nth Heptagonal number
  
// Function to return Nth
// Heptagonal number
function heptagonalNumber($n)
{
    return ((5 * $n * $n) - 
            (3 * $n)) / 2;
}
  
// Driver Code
$n = 2;
echo heptagonalNumber($n), "\n";
$n = 15;
echo heptagonalNumber($n);
  
// This code is contributed 
// by anuj_67.
?>

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Output :

7
540

Reference: https://en.wikipedia.org/wiki/Heptagonal_number



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