This turing machine recognizes {0^n1^n | n>= 0}
(0  6r
(00x1r
(1001r
(1111r
(1xx2l
(1  2l                See Gersting, p473
(21x3l
(3113l
(3004l
(3xx5r
(4004l
(4xx0r
(5xx6r