Calculer: \[ D_n = \begin{vmatrix} 0 & 1 & 2 & \cdots & n \\ 1 & 0 & 1 & \ddots & \vdots \\ 2 & 1 & 0 & \ddots & 2 \\ \vdots & \ddots & \ddots & \ddots & 1 \\ n & \cdots & 2 & 1 & 0 \end{vmatrix}_{[n+1]} \]