Given a number n, find the** nth **Centered decagonal number .

A **Centered Decagonal Number** is centered figurative number that represents a decagon with dot in center and all other dot surrounding it in successive decagonal form. Source[Wiki].

The first few Centered Decagonal Numbers are :

1, 11, 31, 61, 101, 151, 211, 281, 361, 451, 551, 661…………**Examples :**

Input : 3 Output : 31 Input : 6 Output : 151

In mathematics centered decagonal number for** n-th **term is given by :

Below is the basic implementation of the above idea.

## C++

`// Program to find nth` `// centered decagonal` `// number` `#include <bits/stdc++.h>` `using` `namespace` `std;` `// Centered decagonal` `// number function` `int` `centereddecagonalnum(` `int` `n)` `{` ` ` `// Formula to calculate nth` ` ` `// centered decagonal number &` ` ` `// return it into main function.` ` ` `return` `(5 * n * n + 5 * n + 1);` `}` `// Driver Code` `int` `main()` `{` ` ` `int` `n = 5;` ` ` `cout << n << ` `"th centered decagonal"` ` ` `<< ` `"number: "` `;` ` ` `cout << centereddecagonalnum(n);` ` ` `cout << endl;` ` ` `n = 9;` ` ` `cout << n << ` `"th centered decagonal"` ` ` `<< ` `"number: "` `;` ` ` `cout << centereddecagonalnum(n);` ` ` `return` `0;` `}` |

## Java

`// Java Program to find nth` `// centered decagonal number` `import` `java.io.*;` `class` `GFG` `{` ` ` ` ` `// Centered decagonal` ` ` `// number function` ` ` `static` `int` `centereddecagonalnum(` `int` `n)` ` ` `{` ` ` ` ` `// Formula to calculate nth` ` ` `// centered decagonal number &` ` ` `// return it into main function.` ` ` `return` `(` `5` `* n * n + ` `5` `* n + ` `1` `);` ` ` `}` ` ` `// Driver Code` ` ` `public` `static` `void` `main (String[] args)` ` ` `{` ` ` `int` `n = ` `5` `;` ` ` `System.out.print(n + ` `"th centered "` `+` ` ` `"decagonal number: "` `);` ` ` `System.out.println(centereddecagonalnum(n));` ` ` `n = ` `9` `;` ` ` `System.out.print(n + ` `"th centered "` `+` ` ` `"decagonal number: "` `);` ` ` `System.out.println(centereddecagonalnum(n));` ` ` `}` `}` `// This code is contributed by m_kit` |

## Python3

`# Program to find nth` `# centered decagonal number` `# Centered decagonal` `# number function` `def` `centereddecagonalnum(n) :` ` ` ` ` `# Formula to calculate` ` ` `# nth centered decagonal` ` ` `# number & return it` ` ` `# into main function.` ` ` `return` `(` `5` `*` `n ` `*` `n ` `+` ` ` `5` `*` `n ` `+` `1` `)` `# Driver Code` `if` `__name__ ` `=` `=` `'__main__'` `:` ` ` ` ` `n ` `=` `5` ` ` `print` `(n,` `"th centered decagonal "` `+` ` ` `"number : "` `,` ` ` `centereddecagonalnum(n))` ` ` `n ` `=` `9` ` ` `print` `(n,` `"th centered decagonal "` `+` ` ` `"number : "` `,` ` ` `centereddecagonalnum(n))` ` ` `# This code is contributed by m_kit` |

## C#

`// Program to find nth` `// centered decagonal` `// number` `using` `System;` `class` `GFG` `{` `// Centered decagonal` `// number function` `static` `int` `centereddecagonalnum(` `int` `n)` `{` ` ` `// Formula to calculate nth` ` ` `// centered decagonal number &` ` ` `// return it into main function.` ` ` `return` `(5 * n * n + 5 * n + 1);` `}` `// Driver Code` `static` `public` `void` `Main ()` `{` `int` `n = 5;` `Console.Write(n + ` `"th centered decagonal"` `+` ` ` `"number: "` `);` `Console.WriteLine(centereddecagonalnum(n));` `n = 9;` `Console.Write(n + ` `"th centered decagonal"` `+` ` ` `"number: "` `);` `Console.WriteLine(centereddecagonalnum(n));` `}` `}` `// This code is contributed by aj_36` |

## PHP

`<?php` `// Program to find nth` `// centered decagonal number` `// Centered decagonal` `// number function` `function` `centereddecagonalnum(` `$n` `)` `{` ` ` `// Formula to calculate` ` ` `// nth centered decagonal` ` ` `// number & return it` ` ` `// into main function.` ` ` `return` `(5 * ` `$n` `* ` `$n` `+` ` ` `5 * ` `$n` `+ 1);` `}` `// Driver Code` `$n` `= 5;` `echo` `$n` `, ` `"th centered decagonal"` `,` ` ` `"number: "` `;` `echo` `centereddecagonalnum(` `$n` `);` `echo` `"\n"` `;` `$n` `= 9;` `echo` `$n` `, ` `"th centered decagonal"` `,` ` ` `"number: "` `;` `echo` `centereddecagonalnum(` `$n` `);` `// This code is contributed by ajit` `?>` |

## Javascript

`<script>` `// Javascript Program to find nth` `// centered decagonal number` `// Centered decagonal` `// number function` `function` `centereddecagonalnum(n)` `{` ` ` ` ` `// Formula to calculate nth` ` ` `// centered decagonal number &` ` ` `// return it into main function.` ` ` `return` `(5 * n * n + 5 * n + 1);` `}` `// Driver Code` `var` `n = 5;` `document.write(n + ` `"th centered "` `+` ` ` `"decagonal number: "` `);` `document.write(centereddecagonalnum(n) + ` `"<br>"` `);` `n = 9;` `document.write(n + ` `"th centered "` `+` ` ` `"decagonal number: "` `);` `document.write(centereddecagonalnum(n));` `// This code is contributed by Kirti` ` ` `</script>` |

**Output**

5th centered decagonalnumber: 151 9th centered decagonalnumber: 451

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