Here in this article, we have provided a python source code that can find the sum of the first n natural numbers using recursion technique.

**Prerequisite topics to create this program.**

- Python Input, Output
- Python User-Defined Function
- Python Recursion
- Python if…else statements

**Steps:**

- First, ask the user to enter a number.
- create a function in which, with each recursion, we decrease the number value by one.
- And add the decremented number with the actual number itself.

**Python Program to Find Sum of Natural Numbers Using Recursion**

**Code:**

def first_sum(n): if n <= 1: return n else: #recursion return n + first_sum(n-1) num = int(input("Enter the Number: ")) if num > 0: print("The sum of first", num, "is ",first_sum(num)) else: print("Please Enter a valid number")

**Output 1:**

Enter the Number: 18 The sum of first 18 is 171

Output 2:Enter the Number: 4 The sum of first 4 is 10

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