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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 2 |
| 5 | 4 |
| 6 | 12 |
| 7 | 60 |
| 8 | 420 |
| 9 | 6720 |
| 10 | 241920 |
| 11 | 27336960 |
| 12 | 15773425920 |
| 13 | 64182070068480 |
| 14 | 4184799332605032960 |
| 15 | 9825130460280752853949440 |
| 16 | 2606675287692747620296839987164160 |
| 17 | 399035505430293222012069797891526139192304640 |
[1,1,1,1,2,4,12,60,420,6720,241920,27336960, 15773425920,64182070068480,4184799332605032960, 9825130460280752853949440, 2606675287692747620296839987164160, 399035505430293222012069797891526139192304640] |