( )13.
【Min Yue Chen】評論
f(1) = 1 * f(1-1) = 1 * 1 = 1f(2) = 2 * f(2-1) = 2 * 1 = 2f(3) = 3 * f(3-1) = 3 * 2 = 6f(4) = 4 * f(4-1) = 4 * 6 = 24