Mathematica, how to construct a tridiagonal matrix?

Hello I want to view the entries of a block tridiagonal matrix. The matrix is defined by

and

I want to examine the structure of this matrix. Obviously writing this out by hand is a laborious task so I was wondering if mathematica can help me.

I tried

Table[Subscript[u, i, j - 1] + Subscript[u, i - 1, j] +

4 Subscript[u, i, j] + Subscript[u, i + 1, j] + Subscript[u, i,

j + 1] - h^2 Subscript[f, i, j], {i, 3}, {j, 4}]

But this doesn't quite output what I want. Can somebody tell me how I can construct this matrix more explicitly in Mathematica?