Python Program to Find Sum of Natural Numbers by Recursion

This Python program finds the sum of first n natural numbers using a recursive function or recursion.

Python Source Code: Sum of Natural Numbers Using Recursion

# Sum of first n natural numbers using recusrion

# Recursive function definition
def rec_sum(n):
    s = 0
    if n<=0:
        return 0
    return n + rec_sum(n-1)

# Reading number from user
number = int(input('Enter number: '))

# Displaying sum of first n natural numbers
print('Sum of first %d natural numbers is %d' %(number,rec_sum(number)))

The output of the above program is:

Enter number: 20
Sum of first 20 natural numbers is 210