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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 6 |
| 3 | 105 |
| 4 | 27030 |
| 5 | 1771476585 |
| 6 | 7608434000728254870 |
| 7 | 140350834813144189858090274002849666665 |
| 8 | 47758914269546354982683078068829456704164423862093743397580034411621752859030 |
[0,1,6,105,27030,1771476585,7608434000728254870, 140350834813144189858090274002849666665, 47758914269546354982683078068829456704164423862093\ 743397580034411621752859030] |