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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 2 |
| 3 | 12 |
| 4 | 504 |
| 5 | 22320 |
| 6 | 1521360 |
| 7 | 140394240 |
| 8 | 17034433920 |
| 9 | 2627788262400 |
| 10 | 502511002156800 |
| 11 | 116684130094963200 |
| 12 | 32342603041381248000 |
[0,2,12,504,22320,1521360,140394240,17034433920, 2627788262400,502511002156800,116684130094963200, 32342603041381248000] |