# Find the sum of the first N Dodecagonal Numbers

Last Updated : 23 Nov, 2022

Given a number N the task is to find the sum of first N Dodecagonal Number.

The first few dodecagonal numbers are 1, 12, 33, 64, 105, 156, 217 …

Examples:

Input: N = 3
Output: 46
Explanation:
1, 12 and 33 are the first three Dodecagonal numbers

Input: N = 5
Output: 215

Approach:

1. Initially, we need to create a function that will help us to calculate the Nth Dodecagonal number.
2. Run a loop starting from 1 to N, to find ith Dodecagonal number.
3. Add all the above calculated Dodecagonal numbers.
4. Finally, display the sum of the first N Dodecagonal numbers.

Below is the implementation of the above approach:

## C++

 `// C++ program to find the sum of` `// the first N dodecagonal numbers` `#include ` `using` `namespace` `std;`   `// Function to find the N-th` `// dodecagonal number` `int` `Dodecagonal_num(``int` `n)` `{`   `    ``// Formula to calculate N-th` `    ``// dodecagonal number` `    ``return` `(5 * n * n - 4 * n);` `}`   `// Function to find the sum of ` `// the first N dodecagonal numbers` `int` `sum_Dodecagonal_num(``int` `n)` `{`   `    ``// Variable to get the sum` `    ``int` `summ = 0;`   `    ``// Iterating through the` `    ``// first N numbers` `    ``for``(``int` `i = 1; i < n + 1; i++)` `    ``{` `        `  `        ``// Compute the sum` `        ``summ += Dodecagonal_num(i);` `    ``}` `    ``return` `summ;` `}`   `// Driver Code` `int` `main()` `{` `    ``int` `n = 5;`   `    ``// Display first Nth` `    ``// centered_decagonal number` `    ``cout << (sum_Dodecagonal_num(n));` `    ``return` `0;` `}`   `// This code is contributed by PrinciRaj1992`

## Java

 `// Java program to find the sum of` `// the first N dodecagonal numbers` `class` `GFG {` `    `  `// Function to find the N-th` `// dodecagonal number` `static` `int` `Dodecagonal_num(``int` `n)` `{`   `    ``// Formula to calculate N-th` `    ``// dodecagonal number` `    ``return` `(``5` `* n * n - ``4` `* n);` `}`   `// Function to find the sum of ` `// the first N dodecagonal numbers` `static` `int` `sum_Dodecagonal_num(``int` `n)` `{`   `    ``// Variable to get the sum` `    ``int` `summ = ``0``;`   `    ``// Iterating through the` `    ``// first N numbers` `    ``for``(``int` `i = ``1``; i < n + ``1``; i++)` `    ``{` `       `  `       ``// Compute the sum` `       ``summ += Dodecagonal_num(i);` `    ``}` `    ``return` `summ;` `}`   `// Driver Code` `public` `static` `void` `main(String[] args)` `{` `    ``int` `n = ``5``;`   `    ``// Display first Nth` `    ``// centered_decagonal number` `    ``System.out.println(sum_Dodecagonal_num(n));` `}` `}`   `// This code is contributed by sapnasingh4991`

## Python3

 `# Python3 program to find the ` `# sum of the first N` `# Dodecagonal numbers`   `# Function to find the N-th` `# Dodecagonal number` `def` `Dodecagonal_num(n): `   `    ``# Formula to calculate  ` `    ``# N-th Dodecagonal ` `    ``# number  ` `    ``return` `(``5` `*` `n ``*` `n ``-` `4` `*` `n)` `    `  `  `  `# Function to find the ` `# sum of the first N` `# Dodecagonal numbers ` `def` `sum_Dodecagonal_num(n) : ` `    `  `    ``# Variable to get the sum` `    ``summ ``=` `0` `    `  `    ``# Iterating through the ` `    ``# first N numbers` `    ``for` `i ``in` `range``(``1``, n ``+` `1``):`   `        ``# Compute the sum` `        ``summ ``+``=` `Dodecagonal_num(i)` `    `  `    ``return` `summ` `  `  `# Driver Code ` `if` `__name__ ``=``=` `'__main__'` `: ` `          `  `    ``n ``=` `5` `    `  `    ``print``(sum_Dodecagonal_num(n)) `

## C#

 `// C# program to find the sum of` `// the first N dodecagonal numbers` `using` `System;`   `class` `GFG {` `    `  `// Function to find the N-th` `// dodecagonal number` `static` `int` `Dodecagonal_num(``int` `n)` `{`   `    ``// Formula to calculate N-th` `    ``// dodecagonal number` `    ``return` `(5 * n * n - 4 * n);` `}`   `// Function to find the sum of ` `// the first N dodecagonal numbers` `static` `int` `sum_Dodecagonal_num(``int` `n)` `{`   `    ``// Variable to get the sum` `    ``int` `summ = 0;`   `    ``// Iterating through the` `    ``// first N numbers` `    ``for``(``int` `i = 1; i < n + 1; i++)` `    ``{` `        `  `        ``// Compute the sum` `        ``summ += Dodecagonal_num(i);` `    ``}` `    ``return` `summ;` `}`   `// Driver Code` `public` `static` `void` `Main(String[] args)` `{` `    ``int` `n = 5;`   `    ``// Display first Nth` `    ``// centered_decagonal number` `    ``Console.WriteLine(sum_Dodecagonal_num(n));` `}` `}`   `// This code is contributed by sapnasingh4991`

## Javascript

 ``

Output

`215`

Time Complexity: O(N).
Auxiliary Space: O(1)