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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 6 |
| 3 | 90 |
| 4 | 2510 |
| 5 | 112020 |
| 6 | 7307874 |
| 7 | 655845094 |
| 8 | 77496572328 |
| 9 | 11662893335890 |
| 10 | 2177988280932500 |
[1,6,90,2510,112020,7307874,655845094,77496572328, 11662893335890,2177988280932500] |