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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 3 |
| 5 | 6 |
| 6 | 24 |
| 7 | 148 |
| 8 | 1646 |
| 9 | 34040 |
| 10 | 1358852 |
| 11 | 106321628 |
| 12 | 16006173014 |
| 13 | 4525920859198 |
| 14 | 2404130854745735 |
| 15 | 2426376196165902704 |
| 16 | 4648429222263945620900 |
| 17 | 16788801124652327714275292 |
| 18 | 114722035311851620271616102401 |
[1,1,1,3,6,24,148,1646,34040,1358852,106321628, 16006173014,4525920859198,2404130854745735, 2426376196165902704,4648429222263945620900, 16788801124652327714275292, 114722035311851620271616102401] |