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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 144 |
| 4 | 15390 |
| 5 | 6580224 |
| 6 | 11386265292 |
| 7 | 80284132772352 |
| 8 | 2304717583810291830 |
| 9 | 268613293782939614576640 |
| 10 | 126760224526971269877523841364 |
| 11 | 241675282146473482949215936098066432 |
[1,2,6,144,15390,6580224,11386265292, 80284132772352,2304717583810291830, 268613293782939614576640, 126760224526971269877523841364, 241675282146473482949215936098066432] |