Holt's Linear Model (multiplicative): $$L_t = \alpha Y_t + (1 - \alpha)(\ L_{t-1} * b_{t-1})$$ $$b_t = \beta (L_t / L_{t-1}) + (1 - \beta ) b_{t-1}$$ $$F_t = L_t * b_t m$$

Initialize: \( b_1 = Y_2 / Y_1 \, , \quad L_1 = Y_1 \)