$F_n = F_{n-1} + F_{n-2}$

$F_n = F_{n-1} \times F_{n-2}$

$F_n = F_{n-1} + F_{n-2}$ with $F_0 = 0, F_1 = 1$

$F_n = F_{n-1} + F_{n-2}$ with $F_0 = 1, F_1 = 1$