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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 21 |
| 3 | 1025310 |
| 4 | 393143628567690 |
| 5 | 4161601591128480023923529880 |
| 6 | 3025979870886810157320547152897281546399520600 |
| 7 | 316069513961213168272637175554794298273860325049869267706740636689200 |
[1,21,1025310,393143628567690, 4161601591128480023923529880, 3025979870886810157320547152897281546399520600, 31606951396121316827263717555479429827386032504986\ 9267706740636689200] |