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

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

**Examples**:

Input: N = 5Output: 163

Input: N = 1Output: 3

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

T

_{N}= 2 * 3^{N – 1 }+ 1

**Illustration:**

Input:N = 5Output:163Explanation:

T_{N}= 2 * 3^{N – 1}+ 1

= 2 * 3^{5 – 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 <bits/stdc++.h>` `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

`<script>` ` ` `// JavaScript code for the above approach` ` ` `// Function to return Nth term` ` ` `// of the series` ` ` `function` `calcNum(N) {` ` ` `return` `2 * Math.pow(3, N - 1) + 1;` ` ` `}` ` ` `// Driver Code` ` ` `let N = 5;` ` ` `document.write(calcNum(N));` `// This code is contributed by Potta Lokesh` ` ` `</script>` |

**Output**

163

* Time Complexity:* O(1)

* Auxiliary Space:* O(1)