Octagonal number

You are given a number n, the task is to find nth octagonal number. Also, find the Octagonal series till n.

An octagonal number is the figure number that represent octagonal. Octagonal numbers can be formed by placing triangular numbers on the four sides of a square. Octagonal number is calculated by using the formula (3n2 – 2n).
Examples :

Input : 5
Output : 65

Input : 10
Output : 280

Input : 15
Output : 645



C++

filter_none

edit
close

play_arrow

link
brightness_4
code

// C++ program to find
// nth octagonal number
#include <bits/stdc++.h>
using namespace std;
  
// Function to calculate
//octagonal number
int octagonal(int n)
{
    // Formula for finding 
    // nth octagonal number
    return 3 * n * n - 2 * n;
}
  
// Driver function
int main()
{
    int n = 10;
    cout << n << "th octagonal number :" 
         << octagonal(n);
    return 0;
}

chevron_right


Java

filter_none

edit
close

play_arrow

link
brightness_4
code

// Java program to find
// nth octagonal number
import java.util.*;
import java.lang.*;
  
public class GfG {
  
    // Function to calculate
    //octagonal number
    public static int octagonal(int n)
    {
        // Formula for finding 
        // nth octagonal number
        return 3 * n * n - 2 * n;
    }
  
    // Driver function
    public static void main(String argc[])
    {
        int n = 10;
        System.out.println(n + "th octagonal" +
                     " number :" + octagonal(n));
    }
}
  
/* This code is contributed by Sagar Shukla */

chevron_right


Python

filter_none

edit
close

play_arrow

link
brightness_4
code

# Python program to find 
# nth octagonal number
def octagonal(n):
    return 3 * n * n - 2 * n
  
# Driver code
n = 10
print(n, "th octagonal number :",
       octagonal(n))

chevron_right


C#

filter_none

edit
close

play_arrow

link
brightness_4
code

// C# program to find nth octagonal number
using System;
  
public class GfG {
  
    // Function to calculate
    //octagonal number
    public static int octagonal(int n)
    {
          
        // Formula for finding 
        // nth octagonal number
        return 3 * n * n - 2 * n;
    }
  
    // Driver function
    public static void Main()
    {
        int n = 10;
          
        Console.WriteLine(n + "th octagonal" 
              + " number :" + octagonal(n));
    }
}
  
/* This code is contributed by Vt_m */

chevron_right


PHP

filter_none

edit
close

play_arrow

link
brightness_4
code

<?php
// PHP program to find
// nth octagonal number
  
  
// Function to calculate
//octagonal number
function octagonal($n)
{
      
    // Formula for finding 
    // nth octagonal number
    return 3 * $n * $n - 2 * $n;
}
  
    // Driver Code
    $n = 10;
    echo $n , "th octagonal number :"
                     , octagonal($n);
                       
// This code is contributed by Vt_m .
?>

chevron_right



Output :

10th octagonal number : 280

Given number n, find the octagonal series till n.

We can also find the octagonal series. Octagonal series contains the points on octagonal.

Octagonal series 1, 8, 21, 40, 65, 96, 133, 176, 225, 280, . . .

C++

filter_none

edit
close

play_arrow

link
brightness_4
code

// C++ program to display the 
// octagonal series
#include <bits/stdc++.h>
using namespace std;
  
// Function to display
// octagonal series
void octagonalSeries(int n)
{
    // Formula for finding 
    //nth octagonal number
    for (int i = 1; i <= n; i++) 
  
        // Formula for computing 
        // octagonal number
        cout << (3 * i * i - 2 * i);    
}
  
// Driver function
int main()
{
    int n = 10;
    octagonalSeries(n);
    return 0;
}

chevron_right


Java

filter_none

edit
close

play_arrow

link
brightness_4
code

// Java program to find 
// nth octagonal number
import java.util.*;
import java.lang.*;
   
public class GfG {
   
    // Function to display octagonal series
    public static void octagonalSeries(int n)
    {
        // Formula for finding 
        //nth octagonal number
        for (int i = 1; i <= n; i++)
   
            // Formula for computing
            // octagonal number
            System.out.print(3 * i * i - 2 * i);
    }
   
    // Driver function
    public static void main(String argc[])
    {
        int n = 10;
        octagonalSeries(n);
    }
   
    /* This code is contributed by Sagar Shukla */
}

chevron_right


Python

filter_none

edit
close

play_arrow

link
brightness_4
code

# Python program to find 
# nth octagonal number
def octagonalSeries(n):
    for i in range(1, n + 1):
        print(3 * i * i - 2 * i,
                   end = ", ")
  
# Driver code
n = 10
octagonalSeries(n)

chevron_right


C#

filter_none

edit
close

play_arrow

link
brightness_4
code

// C# program to find 
// nth octagonal number
using System;
  
public class GfG {
  
    // Function to display octagonal series
    public static void octagonalSeries(int n)
    {
          
        // Formula for finding 
        //nth octagonal number
        for (int i = 1; i <= n; i++)
  
            // Formula for computing
            // octagonal number
            Console.Write(3 * i * i - 2 * i + ", ");
    }
  
    // Driver function
    public static void Main()
    {
        int n = 10;
          
        octagonalSeries(n);
    }
}
  
/* This code is contributed by Vt_m */

chevron_right


PHP

filter_none

edit
close

play_arrow

link
brightness_4
code

<?php
// PHP program to display the 
// octagonal series
  
  
// Function to display
// octagonal series
function octagonalSeries($n)
{
      
    // Formula for finding 
    // nth octagonal number
    for ($i = 1; $i <= $n; $i++) 
  
        // Formula for computing 
        // octagonal number
        echo (3 * $i * $i - 2 * $i),","
}
  
    // Driver Code
    $n = 10;
    octagonalSeries($n);
  
// This code is contributed by Vt_m .
?>

chevron_right



Output :

1, 8, 21, 40, 65, 96, 133, 176, 225, 280


My Personal Notes arrow_drop_up

Check out this Author's contributed articles.

If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.



Improved By : vt_m