1?2x3x4x5x6x7x8x9x?n?M=1 N=?1?7?1?2000
1?10?101?2?3?4?5?6?7?8?9?10? 101?02?5?1?0 120?1?2?3?4?19?204?0?101?0201?05?21?015?4?1?0?4?0??
1?1,2,3,...?n
2?
3?n
4?
1?2x3x4x5x6x7x8x9x?n?M=1 N=?1?7?1?2000
1?10?101?2?3?4?5?6?7?8?9?10? 101?02?5?1?0 120?1?2?3?4?19?204?0?101?0201?05?21?015?4?1?0?4?0??
1?1,2,3,...?n
2?
3?n
4?