\[H_{m}(u_{n})=\begin{vmatrix}u_{n}&u_{n+1}&\cdots&u_{n+m-1}\\
u_{n+1}&u_{n+2}&\cdots&u_{n+m}\\
\vdots&\vdots&\ddots&\vdots\\
u_{n+m-1}&u_{n+m}&\cdots&u_{n+2m-2}\end{vmatrix}.\]