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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 120 |
| 6 | 640 |
| 7 | 3924 |
| 8 | 27552 |
| 9 | 197364 |
| 10 | 1677640 |
| 11 | 16002846 |
| 12 | 159888834 |
| 13 | 1733332410 |
| 14 | 19754032288 |
| 15 | 242687959560 |
| 16 | 3279596665638 |
[1,2,6,24,120,640,3924,27552,197364,1677640, 16002846,159888834,1733332410,19754032288, 242687959560,3279596665638] |