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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 60 |
| 5 | 1260 |
| 6 | 239904 |
| 7 | 123263712 |
| 8 | 872883648000 |
| 9 | 35330106763980000 |
| 10 | 15502816844111220549120 |
| 11 | 32196148399600498119169883520 |
| 12 | 2560463149313858442381787649990400000 |
| 13 | 717635502576022020068175045395317927056000000 |
[1,2,6,60,1260,239904,123263712,872883648000, 35330106763980000,15502816844111220549120, 32196148399600498119169883520, 2560463149313858442381787649990400000, 717635502576022020068175045395317927056000000] |