Centered heptagonal number

Given a number n, the task is to find nth Centered heptagonal number.

Centered heptagonal number is centered figure number that represents a heptagon with dot in center and all other dot surrounding in heptagonal form. Nth centered heptagonal number can be calculated by using formula (7n2 – 7n + 2) / 2.

Examples :

Input : n = 2
Output : 8

Input : n = 7
Output : 148

Please refer this diagram for pictorial representation.

Below is the implementation :

C++

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// CPP program to find n-th
// Centered heptagonal number
#include <bits/stdc++.h>
  
using namespace std;
  
// Function to find Centered
// heptagonal number
int centered_heptagonal_num(long int n)
{
    // Formula to calculate nth
    // Centered heptagonal number
    return (7 * n * n - 7 * n + 2) / 2;
}
  
// Driver Code
int main()
{
    long int n = 5;
    cout << n << "th Centered heptagonal number : ";
    cout << centered_heptagonal_num(n);
    return 0;
}

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Java

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// Java program to find n-th Centered
// heptagonal number
import java.io.*;
  
class GFG {
  
    // Function to find Centered heptagonal
    // number
    static long centered_heptagonal_num(long n)
    {
          
        // Formula to calculate nth
        // Centered heptagonal number
        return (7 * n * n - 7 * n + 2) / 2;
    }
      
    // Driver Code
    public static void main (String[] args)
    {
        long n = 5;
        System.out.println( n + "th Centered "
                      + "heptagonal number : "
                + centered_heptagonal_num(n));
    }
}
  
// This code is contributed by anuj_67.

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Python3

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# Python program to find nth
# Centered heptagonal number
  
# Function to find Centered
# heptagonal number
def centered_heptagonal_num(n):
  
    # Formula to calculate nth
    # Centered heptagonal number
    return (7 * n * n - 7 * n + 2) // 2
  
  
# Driver Code
n = 5
print("%sth Centered heptagonal number : " %n,
                    centered_heptagonal_num(n))

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C#

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//C# program to find n-th Centered
// heptagonal number
using System;
  
class GFG {
  
    // Function to find Centered heptagonal
    // number
    static long centered_heptagonal_num(long n)
    {
          
        // Formula to calculate nth
        // Centered heptagonal number
        return (7 * n * n - 7 * n + 2) / 2;
    }
      
    // Driver Code
    public static void Main ()
    {
        long n = 5;
        Console.WriteLine( n + "th Centered "
                    + "heptagonal number : "
                + centered_heptagonal_num(n));
    }
}
  
// This code is contributed by anuj_67.

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PHP

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<?php
// PHP program to find n-th
// Centered heptagonal number
  
// Function to find Centered
// heptagonal number
function centered_heptagonal_num($n)
{
    // Formula to calculate nth
    // Centered heptagonal number
    return (7 * $n * $n - 7 * 
                $n + 2) / 2;
}
  
// Driver Code
$n = 5;
echo $n ,"th Centered heptagonal number : ";
echo centered_heptagonal_num($n);
  
// This code is contributed by m_kit
?>

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Output :

5th Centered heptagonal number : 71


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