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
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++
// 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;
}
// C program to find the
// nth Heptagonal number
#include <stdio.h>
// Function to return Nth Heptagonal
// number
int heptagonalNumber(int n)
{
return ((5 * n * n) - (3 * n)) / 2;
}
// Drivers Code
int main()
{
int n = 2;
printf("%d\n",heptagonalNumber(n));
n = 15;
printf("%d\n",heptagonalNumber(n));
return 0;
}
// This code is contributed by kothavvsaakash.
// 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.
# 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
// 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.
<?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.
?>
<script>
// Javascript program to find the
// nth Heptagonal number
// Function to return Nth Heptagonal
// number
function heptagonalNumber(n)
{
return parseInt(((5 * n * n) - (3 * n)) / 2);
}
// Drivers Code
let n = 2;
document.write(heptagonalNumber(n) + "<br>");
n = 15;
document.write(heptagonalNumber(n) + "<br>");
// This code is contributed by rishavmahato348.
</script>
Time Complexity: O(1), since there is no loop or recursion.
Auxiliary Space: O(1), since no extra space has been taken.
Reference: https://en.wikipedia.org/wiki/Heptagonal_number