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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 16 |
| 4 | 120 |
| 5 | 1200 |
| 6 | 15078 |
| 7 | 228984 |
| 8 | 4085028 |
| 9 | 83795085 |
| 10 | 1943920935 |
| 11 | 50333780640 |
| 12 | 1439208976920 |
| 13 | 45044270036220 |
| 14 | 1531759925038616 |
| 15 | 56239576979827360 |
| 16 | 2217379518189430404 |
| 17 | 93441321290076019236 |
| 18 | 4191262657895865499821 |
[1,3,16,120,1200,15078,228984,4085028,83795085, 1943920935,50333780640,1439208976920, 45044270036220,1531759925038616,56239576979827360, 2217379518189430404,93441321290076019236, 4191262657895865499821] |