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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 3 |
| 4 | 12 |
| 5 | 108 |
| 6 | 2712 |
| 7 | 327240 |
| 8 | 235617840 |
| 9 | 1187514095040 |
| 10 | 47880568312738560 |
| 11 | 17374900629326652478080 |
| 12 | 63050039403700556512496620800 |
[1,1,3,12,108,2712,327240,235617840,1187514095040, 47880568312738560,17374900629326652478080, 63050039403700556512496620800] |