+89 The Fibonacci sequence, is defined by F_0 = 0, F_1 = 1, and F_n = F_{n - 2} + F_{n - 1}. It turns out that
F_n = \frac{\alpha^n - \beta^n}{\sqrt{5}},
where \alpha = \frac{1 + \sqrt{5}}{2} and \beta = \frac{1 - \sqrt{5}}{2}.
The Lucas sequence is defined as follows: L_0 = 2, L_1 = 1, and
L_n = L_{n - 1} + L_{n - 2}
for n \ge 2. What is L_4?
