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# Find the Nth term of the series 1, 3, 7, 15, 31 . . .

Given a positive integer N, the task is to find Nth term of the series:

1, 3, 7, 15, 31, …..

Examples:

Input: N = 5
Output: 31

Input: N = 1
Output: 1

Approach:

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

TN = 2N – 1

Illustration:

Input: N = 5
Output: 31
Explanation:
TN = 2N – 1
= 25 – 1
= 32 – 1
= 31

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` `findTerm(``int` `N)` `{` `    ``return` `pow``(2, N) - 1;` `}`   `// Driver Code` `int` `main()` `{` `    ``int` `N = 5;` `    ``cout << findTerm(N);` `    ``return` `0;` `}`

## Java

 `// Java program to implement` `// the above approach` `import` `java.util.*;`   `public` `class` `GFG` `{`   `  ``// Function to return` `  ``// Nth term of the series` `  ``static` `int` `findTerm(``int` `N)` `  ``{` `    ``return` `(``int``)Math.pow(``2``, N) - ``1``;` `  ``}`   `  ``// Driver Code` `  ``public` `static` `void` `main(String args[])` `  ``{` `    ``int` `N = ``5``;` `    ``System.out.println(findTerm(N));`   `  ``}` `}`   `// This code is contributed by Samim Hossain Mondal.`

## Python

 `# Python program to implement` `# the above approach`   `# Function to return` `# Nth term of the series` `def` `findTerm(N):` `    `  `    ``return` `pow``(``2``, N) ``-` `1`   `# Driver Code` `N ``=` `5` `print``(findTerm(N))`   `# This code is contributed by samim2000.`

## C#

 `// C# program to implement` `// the above approach` `using` `System;`   `class` `GFG` `{`   `  ``// Function to return` `  ``// Nth term of the series` `  ``static` `int` `findTerm(``int` `N)` `  ``{` `    ``return` `(``int``)Math.Pow(2, N) - 1;` `  ``}`   `  ``// Driver Code` `  ``public` `static` `void` `Main()` `  ``{` `    ``int` `N = 5;` `    ``Console.Write(findTerm(N));`   `  ``}` `}`   `// This code is contributed by Samim Hossain Mondal.`

## Javascript

 ``

Output

`31`

Time Complexity: O(logN) since using inbuilt pow function

Auxiliary Space: O(1)

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