Description

The bug occurs in a recursive factorial function that incorrectly throws an exception when n is less than 20, instead of when n exceeds 20.

Expected behavior

• The function should return the factorial of n for valid inputs between 0 and 20, inclusive.
• If n > 20, an exception should be thrown indicating that the maximum allowable value is 20.

Actual behavior

• The function currently throws an exception if n < 20, which is incorrect.
• Input values of n > 20 are allowed, potentially leading to integer overflow.

Steps to reproduce

• Call factorial(10) or any n less than 20. The function incorrectly throws an exception.
• Call factorial(25). No exception is thrown, but the value is incorrect or may result in integer overflow.

Context

• The function is designed to calculate the factorial of a number n using recursion.
• The valid range of n for uint64_t is 0 <= n <= 20 because the factorial of numbers larger than 20 exceeds the maximum value of a uint64_t.

Additional information

No response