Tridiagonal matrix

Definition

It is a square matrix where all elements except the diagonal, sub-diagonal and super-diagonal elements are zero i.e. $a_{ij} = 0$ for $∣ i - j ∣ > 1$

A = a_{1} b_{2} c_{1} a_{2} ⋱ c_{2} ⋱ ⋱ ⋱ ⋱ b_{n} c_{n - 1} a_{n}