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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 0 |
| 3 | 3 |
| 4 | 2 |
| 5 | 30 |
| 6 | 0 |
| 7 | 3000 |
| 8 | 20160 |
| 9 | 19571328 |
| 10 | 8136806400 |
| 11 | 13826847640320 |
| 12 | 113788019281305600 |
[1,0,3,2,30,0,3000,20160,19571328,8136806400, 13826847640320,113788019281305600] |