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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 22 |
| 4 | 181 |
| 5 | 7845 |
| 6 | 755338 |
| 7 | 182232300 |
| 8 | 122868970059 |
| 9 | 214646199763320 |
[1,1,22,181,7845,755338,182232300,122868970059, 214646199763320] |