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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 12 |
| 4 | 80 |
| 5 | 560 |
| 6 | 4032 |
| 7 | 29568 |
| 8 | 219648 |
| 9 | 1647360 |
| 10 | 12446720 |
| 11 | 94595072 |
| 12 | 722362368 |
[1,2,12,80,560,4032,29568,219648,1647360,12446720, 94595072,722362368] |