# Program to find Nth odd Fibonacci Number

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 omited even terms from the general fibonacci sequence.

Examples:

```Input: N = 3
Output: 3

Input: N = 4
Output: 5
```

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

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 fibonaci number ` ` `  `#include ` `using` `namespace` `std; ` ` `  `// Function to find nth odd fibonaci 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 fibonaci number  ` `class` `GFG  ` `{ ` `     `  `    ``// Function to find nth odd fibonaci 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 fibonaci number ` ` `  `# Function to find nth odd fibonaci 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 fibonaci number  ` `using` `System; ` `     `  `class` `GFG  ` `{ ` `     `  `    ``// Function to find nth odd fibonaci 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 `

Output:

```5
```

Time Complexity: O(N)

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