Logic Building/Phase 3 - Level 1: Basic Recursion/Program

Sum of First N Natural Numbers Recursively

Calculate sum of first n natural numbers recursively.

Logic BuildingIntermediate

Logic Building

def sum_natural(n):
    # Base case
    if n == 0:
        return 0
    
    # Recursive case
    return n + sum_natural(n - 1)

# Test
n = int(input("Enter n: "))
result = sum_natural(n)
print(f"Sum: {result}")

Output

Enter n: 5
Sum: 15

Sum(n) = n + Sum(n-1).

Key Concepts:

Base case: sum(0) = 0
Recursive: n + sum of n-1
Accumulate as recursion unwinds

Odd Numbers 1-N Recursively

Power x^n Recursively