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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 7 |
| 3 | 56 |
| 4 | 918 |
| 5 | 37050 |
| 6 | 2753404 |
| 7 | 389403912 |
| 8 | 111681916203 |
| 9 | 65358224695742 |
[0,7,56,918,37050,2753404,389403912,111681916203, 65358224695742] |