Given a number n, find the nth Centered Hexadecagonal Number.

A Centered Hexadecagonal number represents a dot in the centre and other dots around it in successive hexadecagonal(16 sided polygon) layers. The first few Centered Hexadecagonal numbers are:
1, 17, 49, 97, 161, 241, 337, 449, 577, 721, 881………………….

Examples :

```Input :  3
Output : 49

Input : 10
Output : 721
```

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

In mathematics, Centered hexadecagonal number for the n-th term is given by :

` `

Below is the basic implementation of the above idea:

## C++

 `// C++ Program to find ` `// nth centered hexadecagonal ` `// number ` `#include ` `using` `namespace` `std; ` ` `  `// centered hexadecagonal function ` `int` `center_hexadecagonal_num(``long` `int` `n) ` `{ ` `    ``// Formula to calculate nth ` `    ``// centered hexadecagonal number ` `    ``return` `8 * n * n - 8 * n + 1; ` `} ` ` `  `// Driver Code ` `int` `main() ` `{ ` `    ``long` `int` `n = 2; ` `    ``cout << n << ``"th centered hexadecagonal number : "`  `                    ``<< center_hexadecagonal_num(n); ` `    ``cout << endl; ` `    ``n = 12; ` `    ``cout << n << ``"th centered hexadecagonal numbe : "` `                    ``<< center_hexadecagonal_num(n); ` ` `  `    ``return` `0; ` `} `

## Java

 `// Java Program to find nth ` `// centered hexadecagonal number ` `import` `java.io.*; ` ` `  `class` `GFG  ` `{ ` `    ``// centered hexadecagonal function ` `    ``static` `int` `center_hexadecagonal_num(``int` `n) ` `    ``{ ` `        ``// Formula to calculate nth ` `        ``// centered hexadecagonal number ` `        ``return` `8` `* n * n -  ` `               ``8` `* n + ``1``; ` `    ``} ` `     `  `    ``// Driver Code ` `    ``public` `static` `void` `main(String args[]) ` `    ``{ ` `        ``int` `n = ``2``; ` `        ``System.out.print(n + ``"th centered "` `+ ` `                    ``"hexadecagonal number: "``); ` `        ``System.out.println(center_hexadecagonal_num(n)); ` `         `  `        ``n = ``12``; ` `        ``System.out.print(n + ``"th centered "` `+ ` `                    ``"hexadecagonal number: "``); ` `        ``System.out.println(center_hexadecagonal_num(n)); ` `    ``} ` `} ` ` `  `// This code is contributed by ajit. `

## Python3

 `# Program to find nth  ` `# centered hexadecagonal  ` `# number ` ` `  `# centered hexadecagonal  ` `# function ` `def` `center_hexadecagonal_num(n): ` `     `  `    ``# Formula to calculate  ` `    ``# nth centered hexadecagonal ` `    ``# number ` `    ``return` `8` `*` `n ``*` `n ``-` `8` `*` `n ``+` `1` ` `  `# Driver Code ` `if` `__name__ ``=``=` `'__main__'` `: ` `         `  `    ``n ``=` `2` `    ``print``(n,``"nd centered hexadecagonal "` `+`  `                              ``"number : "``, ` `              ``center_hexadecagonal_num(n)) ` `    ``n ``=` `12` `    ``print``(n,``"th centered hexadecagonal "` `+`  `                              ``"number : "``, ` `              ``center_hexadecagonal_num(n)) ` `                 `  `# This code is contributed ` `# by akt_mit `

## C#

 `// C# Program to find nth ` `// centered hexadecagonal number ` `using` `System; ` ` `  `class` `GFG ` `{ ` `     `  `    ``// centered hexadecagonal ` `    ``// function ` `    ``static` `int` `center_hexadecagonal_num(``int` `n) ` `    ``{ ` `        ``// Formula to calculate nth ` `        ``// centered hexadecagonal number ` `        ``return` `8 * n * n -  ` `               ``8 * n + 1; ` `    ``} ` `     `  `    ``// Driver Code ` `    ``static` `public` `void` `Main () ` `    ``{ ` `        ``int` `n = 2; ` `        ``Console.Write(n + ``"th centered "` `+ ` `                    ``"hexadecagonal number: "``); ` `        ``Console.WriteLine(center_hexadecagonal_num(n)); ` `         `  `        ``n = 12; ` `        ``Console.Write(n + ``"th centered "` `+ ` `                    ``"hexadecagonal number: "``); ` `        ``Console.WriteLine(center_hexadecagonal_num(n)); ` `    ``} ` `} ` ` `  `// This code is contributed by m_kit `

## PHP

 ` `

Output :

```2th centered hexadecagonal number : 17
12th centered hexadecagonal numbe : 1057
```

References:
http://oeis.org/A069129

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