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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 18 |
| 3 | 165 |
| 4 | 2016 |
| 5 | 30783 |
| 6 | 564048 |
| 7 | 12057825 |
| 8 | 294587136 |
| 9 | 8096756763 |
| 10 | 247266851328 |
| 11 | 8306410495485 |
| 12 | 304403359942656 |
| 13 | 12085026305182743 |
| 14 | 516690458532292608 |
| 15 | 23668814542820609145 |
| 16 | 1156515067746149400576 |
| 17 | 60041982382475841900723 |
| 18 | 3300519734382436473765888 |
[1,3,18,165,2016,30783,564048,12057825,294587136, 8096756763,247266851328,8306410495485, 304403359942656,12085026305182743, 516690458532292608,23668814542820609145, 1156515067746149400576,60041982382475841900723, 3300519734382436473765888] |