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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 2 |
| 3 | 16108 |
| 4 | 730983420 |
| 5 | 102117302729744 |
| 6 | 36724170744914466520 |
| 7 | 29526013062983124375791088 |
[0,2,16108,730983420,102117302729744, 36724170744914466520,29526013062983124375791088] |