In sequence an, A1 = 1, A3 = 7, and a (n + 1) = nan-1 / (n-1), find the general term formula of an

In sequence an, A1 = 1, A3 = 7, and a (n + 1) = nan-1 / (n-1), find the general term formula of an

The equation is changed into a (n + 1) / an-1 = n / (n-1), an / An-2 = n-1 / n-2, a3-a1 = 2 / 1, and then all the formulas are multiplied