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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 120 |
| 6 | 272 |
| 7 | 1904 |
| 8 | 15232 |
| 9 | 124800 |
| 10 | 848640 |
| 11 | 7507200 |
| 12 | 39738368 |
| 13 | 433441792 |
| 14 | 2589116416 |
| 15 | 30419859456 |
| 16 | 486717751296 |
| 17 | 8128101580800 |
| 18 | 132557598294016 |
| 19 | 1971862458400768 |
| 20 | 30421253686034432 |
| 21 | 512675443057623040 |
| 22 | 7176891455747129344 |
| 23 | 130521457800367308800 |
[1,1,2,6,24,120,272,1904,15232,124800,848640, 7507200,39738368,433441792,2589116416,30419859456, 486717751296,8128101580800,132557598294016, 1971862458400768,30421253686034432, 512675443057623040,7176891455747129344, 130521457800367308800] |