1. The problem is to find the easiest way to compute the factorial of a number $n$, denoted as $n!$. 2. The factorial of a non-negative integer $n$ is defined as the product of all positive integers less than or equal to $n$: $$n! = n \times (n-1) \times (n-2) \times \cdots \times 2 \times 1$$ 3. Important rules: - $0!$ is defined as 1. - Factorials grow very fast as $n$ increases. 4. The easiest way to compute factorials for small numbers is to multiply all integers from 1 up to $n$ step-by-step. 5. For larger numbers, using a calculator or programming functions (like Python's math.factorial) is efficient. 6. Example: Compute $5!$ step-by-step: $$5! = 5 \times 4 \times 3 \times 2 \times 1 = 120$$ 7. Summary: For manual calculation, multiply all integers from 1 to $n$. For large $n$, use computational tools.