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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 20 |
| 3 | 1635 |
| 4 | 339708 |
| 5 | 143060850 |
| 6 | 106681715484 |
| 7 | 128573202886349 |
| 8 | 234439539245241093 |
[1,20,1635,339708,143060850,106681715484, 128573202886349,234439539245241093] |