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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 8 |
| 3 | 48 |
| 4 | 352 |
| 5 | 3008 |
| 6 | 29440 |
| 7 | 324096 |
| 8 | 3947520 |
| 9 | 52541440 |
| 10 | 757260288 |
| 11 | 11733385216 |
| 12 | 194272854016 |
| 13 | 3419584921600 |
| 14 | 63707979972608 |
| 15 | 1251489089060864 |
| 16 | 25836869372608512 |
| 17 | 558946705406427136 |
| 18 | 12638569755079344128 |
| 19 | 298003073694026432512 |
| 20 | 7312035980392431353856 |
[1,2,8,48,352,3008,29440,324096,3947520,52541440, 757260288,11733385216,194272854016,3419584921600, 63707979972608,1251489089060864,25836869372608512, 558946705406427136,12638569755079344128, 298003073694026432512,7312035980392431353856] |