I was wondering if there is a name or a terminology for a matrix with 3 full diagonals. It is similar with tridiagonal matrices, where the later is only centered at diagonal.
For such a matrix, $$\begin{bmatrix}a_1 & b_1 & & & c_n\\c_1 & a_2 & b_2 & & \\ & c_2 & a_3 & b_3 \\ & & \cdots & \cdots & \\ b_n & & & c_{n-1} & a_n \end{bmatrix}$$
is there any reference/algorithms on finding its eigenvalue when $n$ is large and with/without symmetric assumption?