def fibonacci(n):
    if n <= 0:
        return []
    if n == 1:
        return [0]
    let result = [0, 1]
    for i in range(2, n):
        result.append(result[i - 1] + result[i - 2])
    return result

def main():
    let n = 20
    let fibs = fibonacci(n)
    print(f'First {n} Fibonacci numbers:')
    for i in range(len(fibs)):
        print(f'  F({i}) = {fibs[i]}')

    # Demonstrate list comprehension
    let evens = [x for x in fibs if x % 2 == 0]
    print(f'Even Fibonacci numbers: {evens}')

    # Demonstrate sum using reduce-like pattern
    let total = 0
    for x in fibs:
        total += x
    print(f'Sum of first {n} Fibonacci numbers: {total}')

main()