CLAPACK_PRB3
  Demonstrate the use of DGBTRF to factor a banded matrix
  and DGBTRS to solve an associated linear system
  using double precision real arithmetic.

  Coefficient matrix:

               2              -1               0               0
              -1               2              -1               0
               0              -1               2              -1
               0               0              -1               2

  Right hand side:

               0
               0
               0
               5

  Computed solution:

               1
               2
               3
               4