public void Factorial()
{
Assert.AreEqual(1u, NumberSequence.Factorial(0));
Assert.AreEqual(1u, NumberSequence.Factorial(1));
Assert.AreEqual(2u, NumberSequence.Factorial(2));
Assert.AreEqual(120u, NumberSequence.Factorial(5));
Assert.AreEqual(3628800u, NumberSequence.Factorial(10));
Assert.AreEqual(2432902008176640000u, NumberSequence.Factorial(20));
}