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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 15 |
| 4 | 212 |
| 5 | 3712 |
| 6 | 96256 |
| 7 | 3423168 |
| 8 | 158521536 |
| 9 | 8362014912 |
| 10 | 635861560320 |
| 11 | 51551078842368 |
[1,3,15,212,3712,96256,3423168,158521536, 8362014912,635861560320,51551078842368] |