band1_backsolve_vec: Backsolve with band 1 upper Cholesky.
Description
Backsolve with band 1 upper Cholesky.
Usage
band1_backsolve_vec(U, z)
Arguments
U
An upper triangular square matrix with non-zero entries only on the
main diagonal and the first superdiagonal.
z
A vector with as many elements as the number of rows of U.