n=4的一些解决方案:
..6....6....6....4....4....1....4....1....4....4....4....4....1....6....1....6
..2....2....4....6....6....5....5....5....2....2....6....2....3....4....5....4
..6....7....2....4....2....3....3....6....4....6....2....3....2....6....4....2
..4....1....4....6....4....1....6....4....6....4....6....1....4....4....6....6