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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 3 |
| 2 | 25 |
| 3 | 294 |
| 4 | 4566 |
| 5 | 88572 |
| 6 | 2064504 |
| 7 | 56243184 |
| 8 | 1754322480 |
| 9 | 61664980320 |
| 10 | 2412077832000 |
| 11 | 103928089910400 |
| 12 | 4890979939104000 |
| 13 | 249630539076979200 |
| 14 | 13734482066534476800 |
| 15 | 810355993296898406400 |
| 16 | 51040766703826377676800 |
[0,3,25,294,4566,88572,2064504,56243184, 1754322480,61664980320,2412077832000, 103928089910400,4890979939104000, 249630539076979200,13734482066534476800, 810355993296898406400,51040766703826377676800] |