# Program to find Nth odd Fibonacci Number

• Difficulty Level : Easy
• Last Updated : 13 Mar, 2022

Given an integer N. The task is to find the Nth odd Fibonacci number.
The odd number fibonacci series is as:

1, 1, 3, 5, 13, 21, 55, 89, 233, 377, 987, 1597………….and so on.
Note: In the above series we have omitted even terms from the general fibonacci sequence

Examples:

```Input: N = 3
Output: 3

Input: N = 4
Output: 5```

Approach:
On observing carefully, it can be deduced that every third Fibonacci number is even, so the Nth odd Fibonacci number is the {(3*N+1)/2}th term in the general Fibonacci sequence.
Below is the implementation of the above approach:

## C++

 `// C++ program for Nth odd fibonacci number` `#include ``using` `namespace` `std;` `// Function to find nth odd fibonacci number``int` `oddFib(``int` `n)``{``    ``n = (3 * n + 1) / 2;``    ``int` `a = -1, b = 1, c, i;``    ``for` `(i = 1; i <= n; i++) {``        ``c = a + b;``        ``a = b;``        ``b = c;``    ``}``    ``return` `c;``}` `// Driver Code``int` `main()``{``    ``int` `n = 4;``    ` `    ``cout << oddFib(n);``    ` `    ``return` `0;``}`

## Java

 `// Java program for Nth odd fibonacci number``class` `GFG``{``    ` `    ``// Function to find nth odd fibonacci number``    ``static` `int` `oddFib(``int` `n)``    ``{``        ``n = (``3` `* n + ``1``) / ``2``;``        ` `        ``int` `a = -``1``, b = ``1``, c = ``0``, i;``        ` `        ``for` `(i = ``1``; i <= n; i++)``        ``{``            ``c = a + b;``            ``a = b;``            ``b = c;``        ``}``        ``return` `c;``    ``}``    ` `    ``// Driver Code``    ``public` `static` `void` `main (String[] args)``    ``{``        ``int` `n = ``4``;``        ` `        ``System.out.println(oddFib(n));``    ``}``}` `// This code is contributed by AnkitRai01`

## Python3

 `# Python3 program for Nth odd fibonacci number` `# Function to find nth odd fibonacci number``def` `oddFib(n):``    ``n ``=` `(``3` `*` `n ``+` `1``) ``/``/` `2` `    ``a ``=` `-``1``    ``b ``=` `1``    ``c ``=` `0``    ``for` `i ``in` `range``(``1``, n ``+` `1``):``        ``c ``=` `a ``+` `b``        ``a ``=` `b``        ``b ``=` `c` `    ``return` `c` `# Driver Code``n ``=` `4` `print``(oddFib(n))` `# This code is contributed by mohit kumar`

## C#

 `// C# program for Nth odd fibonacci number``using` `System;``    ` `class` `GFG``{``    ` `    ``// Function to find nth odd fibonacci number``    ``static` `int` `oddFib(``int` `n)``    ``{``        ``n = (3 * n + 1) / 2;``        ` `        ``int` `a = -1, b = 1, c = 0, i;``        ` `        ``for` `(i = 1; i <= n; i++)``        ``{``            ``c = a + b;``            ``a = b;``            ``b = c;``        ``}``        ``return` `c;``    ``}``    ` `    ``// Driver Code``    ``public` `static` `void` `Main (String[] args)``    ``{``        ``int` `n = 4;``        ` `        ``Console.WriteLine(oddFib(n));``    ``}``}` `// This code is contributed by 29AjayKumar`

## Javascript

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Output:

`5`

Time Complexity: O(N)

Auxiliary Space: O(1)

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