Logic Building/Phase 3 - Level 2: Advanced Recursion/Program

Sum of First N Even Numbers Recursively

Calculate sum of first n even numbers recursively.

Logic BuildingIntermediate

Logic Building

def sum_even(n):
    # Base case
    if n == 0:
        return 0
    
    # Recursive case
    # nth even number is 2*n
    return (2 * n) + sum_even(n - 1)

# Test
n = int(input("Enter n: "))
result = sum_even(n)
print(f"Sum of first {n} even numbers: {result}")

Output

Enter n: 5
Sum of first 5 even numbers: 30

Nth even number is 2*n.

Key Concepts:

Base case: sum(0) = 0
Nth even number = 2*n
Add current even number to sum of previous

Print Digits in Words

Sum of First N Odd Numbers Recursively