IIRC the number 1 can only be in 3 unique places { 0, 1, 5 } as all other locations are reachable with symmetry. That could reduce the search space with a factor 5.
IIRC the number 1 can only be in 3 unique places { 0, 1, 5 } as all other locations are reachable with symmetry. That could reduce the search space with a factor 5.