
On entry,  ${\mathbf{UPLO}}\ne \text{'L'}$ or $\text{'U'}$. 
On entry,  ${\mathbf{N}}<1$. 
On entry,  ${\mathbf{KD}}<0$. 
On entry,  ${\mathbf{LDAB}}<{\mathbf{KD}}+1$. 
$$\left(\begin{array}{rrrrrrr}5& 4& 1& & & & \\ 4& 6& 4& 1& & & \\ 1& 4& 6& 4& 1& & \\ & 1& 4& 6& 4& 1& \\ & & 1& 4& 6& 4& 1\\ & & & 1& 4& 6& 4\\ & & & & 1& 4& 5\end{array}\right)\text{.}$$ 