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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 15 |
| 4 | 156 |
| 5 | 2032 |
| 6 | 30912 |
| 7 | 737280 |
| 8 | 19491840 |
| 9 | 585019584 |
| 10 | 26539425792 |
| 11 | 1275815411712 |
| 12 | 65050879721472 |
[1,3,15,156,2032,30912,737280,19491840,585019584, 26539425792,1275815411712,65050879721472] |