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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 60 |
| 4 | 1608 |
| 5 | 62520 |
| 6 | 3195360 |
| 7 | 202685760 |
| 8 | 15367129920 |
| 9 | 1356166333440 |
| 10 | 136594585094400 |
| 11 | 15465238193433600 |
| 12 | 1944635519232806400 |
| 13 | 268912358164611532800 |
| 14 | 40563396480486872678400 |
| 15 | 6628655092235188446720000 |
| 16 | 1166636976398869777072128000 |
| 17 | 220020666451278727461672960000 |
[1,4,60,1608,62520,3195360,202685760,15367129920, 1356166333440,136594585094400,15465238193433600, 1944635519232806400,268912358164611532800, 40563396480486872678400,6628655092235188446720000, 1166636976398869777072128000, 220020666451278727461672960000] |