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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 34 |
| 4 | 1020 |
| 5 | 1188106 |
| 6 | 909149847892 |
| 7 | 291200434288840793135801 |
[1,2,6,34,1020,1188106,909149847892, 291200434288840793135801] |