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# Octahedral Number

• Last Updated : 12 Apr, 2021

Given a number n, the task is to find n-th octahedral number.
A octahedral number belongs to a figurate number and it is the number of spheres in an octahedron built from closely packed spheres. First few octahedral numbers (where n = 0, 1, 2, 3…….) are : 0, 1, 6, 19 and so on.
Examples :

Input : 4
Output : 44
Input : 8
Output : 344 Formula for nth octahedral number:

`n * (2n2+1) / 3`

## C++

 `// C++ program to find nth``// octahedral number``#include ``using` `namespace` `std;` `// Function to find``// octahedral number``int` `octahedral_num(``int` `n)``{``    ``// Formula to calculate nth``    ``// octahedral number``    ``return` `n * (2 * n * n + 1) / 3;``}` `// Drivers code``int` `main()``{``    ``int` `n = 5;` `    ``// print result``    ``cout << n << ``"th Octahedral number: "``;``    ``cout << octahedral_num(n);``    ``return` `0;``}`

## Java

 `// Java program to find nth octahedral``// number``import` `java.io.*;` `class` `GFG {` `    ``// Function to find octahedral number``    ``static` `int` `octahedral_num(``int` `n)``    ``{` `        ``// Formula to calculate nth``        ``// octahedral number``        ``// and return it into main function.``        ``return` `n * (``2` `* n * n + ``1``) / ``3``;``    ``}` `    ``// Driver Code``    ``public` `static` `void` `main(String[] args)``    ``{``        ``int` `n = ``5``;``        ``// print result``        ``System.out.print(n + ``"th Octahedral"``                         ``+ ``" number: "``);``        ``System.out.println(octahedral_num(n));``    ``}``}`

## Python3

 `# Python 3 program to find nth``# octahedral number` `# Function to find``# octahedral number``def` `octahedral_num(n) :``    ` `    ``# Formula to calculate nth``    ``# octahedral number``    ``return` `n ``*` `(``2` `*` `n ``*` `n ``+` `1``) ``/``/` `3` `# Driver Code``if` `__name__ ``=``=` `'__main__'` `:``        ` `    ``n ``=` `5``    ``print``(n,``"th Octahedral number: "``                ``, octahedral_num(n))` `# This code is contributed ajit.`

## C#

 `// C# program to find nth``// Octahedral number``using` `System;` `class` `GFG``{``    ` `    ``// Function to find``    ``// octahedral number``    ``static` `int` `octahedral_num(``int` `n)``    ``{` `        ``// Formula to calculate``        ``// nth octahedral number``        ``// and return it into``        ``// main function.``        ``return` `n * (2 * n *``                    ``n + 1) / 3;``    ``}` `    ``// Driver Code``    ``static` `public` `void` `Main ()``    ``{``        ``int` `n = 5;``        ` `        ``// print result``        ``Console.Write(n + ``"th Octahedral"``                        ``+ ``" number: "``);``        ``Console.WriteLine(octahedral_num(n));``    ``}``}` `// This code is Contributed by m_kit`

## PHP

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## Javascript

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Output :

`5th Octahedral number: 85`

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