# Sum of natural numbers using recursion Given a number n, find sum of first n natural numbers. To calculate the sum, we will use a recursive function recur_sum().

Examples :

```Input : 3
Output : 6
Explanation : 1 + 2 + 3 = 6

Input : 5
Output : 15
Explanation : 1 + 2 + 3 + 4 + 5 = 15
```

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

Below is code to find the sum of natural numbers up to n using recursion :

## C++

 `// C++ program to find the  ` `// sum of natural numbers up ` `// to n using recursion ` `#include ` `using` `namespace` `std; ` ` `  `// Returns sum of first  ` `// n natural numbers ` `int` `recurSum(``int` `n) ` `{ ` `    ``if` `(n <= 1) ` `        ``return` `n; ` `    ``return` `n + recurSum(n - 1); ` `} ` ` `  `// Driver code ` `int` `main() ` `{ ` `    ``int` `n = 5; ` `    ``cout << recurSum(n); ` `    ``return` `0; ` `} `

## Java

 `// Java program to find the  ` `// sum of natural numbers up ` `// to n using recursion ` `import` `java.util.*; ` `import` `java.lang.*; ` ` `  `class` `GFG ` `{ ` ` `  `    ``// Returns sum of first  ` `    ``// n natural numbers ` `    ``public` `static` `int` `recurSum(``int` `n) ` `    ``{ ` `        ``if` `(n <= ``1``) ` `            ``return` `n; ` `        ``return` `n + recurSum(n - ``1``); ` `    ``} ` `     `  `    ``// Driver code ` `    ``public` `static` `void` `main(String args[]) ` `    ``{ ` `        ``int` `n = ``5``; ` `        ``System.out.println(recurSum(n)); ` `    ``} ` `} ` ` `  `// This code is contributed by Sachin Bisht `

## Python

 `# Python code to find sum  ` `# of natural numbers upto ` `# n using recursion ` ` `  `# Returns sum of first ` `# n natural numbers ` `def` `recurSum(n): ` `    ``if` `n <``=` `1``: ` `        ``return` `n ` `    ``return` `n ``+` `recurSum(n ``-` `1``) ` ` `  `# Driver code ` `n ``=` `5` `print``(recurSum(n)) `

## C#

 `// C# program to find the  ` `// sum of natural numbers ` `// up to n using recursion ` `using` `System; ` ` `  `class` `GFG ` `{ ` ` `  `    ``// Returns sum of first  ` `    ``// n natural numbers ` `    ``public` `static` `int` `recurSum(``int` `n) ` `    ``{ ` `        ``if` `(n <= 1) ` `            ``return` `n; ` `        ``return` `n + recurSum(n - 1); ` `    ``} ` `     `  `    ``// Driver code ` `    ``public` `static` `void` `Main() ` `    ``{ ` `        ``int` `n = 5; ` `        ``Console.WriteLine(recurSum(n)); ` `    ``} ` `} ` ` `  `// This code is contributed by vt_m `

## PHP

 ` `

Output :

`15 `

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