\left[\matrix{%
1&x_1&{x_1}^2&...&{x_1}^{n-1}\cr
1&x_2&{x_2}^2&...&{x_2}^{n-1}\cr
.&.&.& &.\cr
1&x_n&{x_n}^2&...&{x_n}^{n-1}\cr}\right]