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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 7 |
| 3 | 18 |
| 4 | 61 |
| 5 | 1198 |
| 6 | 13152 |
| 7 | 6492 |
| 8 | 1429403 |
| 9 | 180869894 |
| 10 | 605470336 |
| 11 | 33123913586 |
[0,7,18,61,1198,13152,6492,1429403,180869894, 605470336,33123913586] |