A = size 16 by 16 Matrix of double:
[ 3 -1 0 0 -1 0 0 0 0 0 0 0 0 0 0 0 ]
[ -1 4 -1 0 0 -1 0 0 0 0 0 0 0 0 0 0 ]
[ 0 -1 4 -1 0 0 -1 0 0 0 0 0 0 0 0 0 ]
[ 0 0 -1 3 0 0 0 -1 0 0 0 0 0 0 0 0 ]
[ -1 0 0 0 4 -1 0 0 -1 0 0 0 0 0 0 0 ]
[ 0 -1 0 0 -1 5 -1 0 0 -1 0 0 0 0 0 0 ]
[ 0 0 -1 0 0 -1 5 -1 0 0 -1 0 0 0 0 0 ]
[ 0 0 0 -1 0 0 -1 4 0 0 0 -1 0 0 0 0 ]
[ 0 0 0 0 -1 0 0 0 4 -1 0 0 -1 0 0 0 ]
[ 0 0 0 0 0 -1 0 0 -1 5 -1 0 0 -1 0 0 ]
[ 0 0 0 0 0 0 -1 0 0 -1 5 -1 0 0 -1 0 ]
[ 0 0 0 0 0 0 0 -1 0 0 -1 4 0 0 0 -1 ]
[ 0 0 0 0 0 0 0 0 -1 0 0 0 3 -1 0 0 ]
[ 0 0 0 0 0 0 0 0 0 -1 0 0 -1 4 -1 0 ]
[ 0 0 0 0 0 0 0 0 0 0 -1 0 0 -1 4 -1 ]
[ 0 0 0 0 0 0 0 0 0 0 0 -1 0 0 -1 3 ]

x = size 16 Vector of double:
[ 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 ]

b = A*x = size 16 Vector of double:
[ -4 -2 -1 1 4 6 7 9 8 10 11 13 16 18 19 21 ]

A\b = size 16 Vector of double:
[ 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 ]

euclidean(A\b-x) = 7.11236e-15

