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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 2 |
| 4 | 2 |
| 5 | 10 |
| 6 | 40 |
| 7 | 240 |
| 8 | 5040 |
| 9 | 388080 |
| 10 | 5045040 |
| 11 | 94643905622666400 |
[1,1,2,2,2,10,40,240,5040,388080,5045040, 94643905622666400] |