# Find the Nth term of the series 3, 7, 19, 55, 163, . . .

• Last Updated : 10 Jan, 2022

Given a positive integer N. The task is to find Nth term of the series 3, 7, 19, 55, 163, …..

Examples:

Input: N = 5
Output: 163

Input: N = 1
Output: 3

Approach: The sequence is formed by using the following pattern. For any value N

TN = 2 * 3N – 1 + 1

Illustration:

Input: N = 5
Output: 163
Explanation:
TN = 2 * 3N – 1 + 1
= 2 * 35 – 1 + 1
= 2 * 81 + 1
= 162 + 1
= 163

Below is the implementation of the above approach:

## C++

 `// C++ program to implement` `// the above approach` `#include ` `using` `namespace` `std;`   `// Function to return Nth term` `// of the series` `int` `calcNum(``int` `N)` `{` `    ``return` `2 * ``pow``(3, N - 1) + 1;` `}`   `// Driver Code` `int` `main()` `{` `    ``int` `N = 5;` `    ``cout << calcNum(N);` `    ``return` `0;` `}`

## Java

 `// Java code to implement the above approach` `import` `java.lang.*;` `public` `class` `gfg` `{` `    `  `    ``/* Function to return the Nth term of the series */` `    ``static` `int` `calcNum(``int` `N)` `    ``{` `        ``return` `(``int``)(``2``*(Math.pow(``3``,N-``1``))) + ``1` `;` `    ``}`   `    ``// Driver Code` `    ``public` `static` `void` `main(String[] args)` `    ``{` `        ``int` `N = ``5``;`   `        ``System.out.println(calcNum(N));` `    ``}` `}`   `// This code is contributed by Abhishek Thakur`

## Python3

 `# Python3 program to implement` `# the above approach`   `# Function to return Nth term` `# of the series` `def` `calcNum(N):` `    `  `    ``return` `2` `*` `(``3` `*``*` `(N ``-` `1``)) ``+` `1`   `# Driver Code` `N ``=` `5`   `print``(calcNum(N))`   `# This code is contributed by gfgking`

## C#

 `// C# code to implement the above approach` `using` `System;` `public` `class` `gfg` `{`   `  ``/* Function to return the Nth term of the series */` `  ``static` `int` `calcNum(``int` `N)` `  ``{` `    ``return` `(``int``)(2 * (Math.Pow(3, N - 1))) + 1;` `  ``}`   `  ``// Driver Code` `  ``public` `static` `void` `Main(``string``[] args)` `  ``{` `    ``int` `N = 5;`   `    ``Console.WriteLine(calcNum(N));` `  ``}` `}`   `// This code is contributed by Abhishek Thakur`

## Javascript

 ``

Output

`163`

Time Complexity: O(1)

Auxiliary Space: O(1)

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