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Centered heptagonal number
• Last Updated : 07 Apr, 2021

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++

 `// CPP program to find n-th``// Centered heptagonal number``#include ` `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;``}`

## Java

 `// 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.`

## Python3

 `# 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))`

## C#

 `//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.`

## PHP

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## Javascript

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Output :

`5th Centered heptagonal number : 71`

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