# 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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