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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 12 |
| 5 | 168 |
| 6 | 240 |
| 7 | 14880 |
| 8 | 65280 |
| 9 | 4294901760 |
| 10 | 7608944640 |
| 11 | 1125874137169920 |
| 12 | 18446744069414584320 |
[1,2,6,12,168,240,14880,65280,4294901760, 7608944640,1125874137169920,18446744069414584320] |