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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 6 |
| 3 | 600 |
| 4 | 210 |
| 5 | 866250 |
| 6 | 15732957240 |
| 7 | 156225655145328088320 |
| 8 | 7121261709511950 |
[2,6,600,210,866250,15732957240, 156225655145328088320,7121261709511950] |