为什么这个开立方的小程序运行不了呢 求助

Private Sub conmandl_click()
Dim x(2)
a = 7: x(1) = 2
For n = 1 To 10
x(2) = 2 / 3 * x(1) + a / (3 + (x(i)) ^ 2)
Print x(2)
x(1) = x(2)
Next
End Sub