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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 6 |
| 5 | 27 |
| 6 | 2910 |
| 7 | 671418 |
| 8 | 5925456572864 |
| 9 | 1819432729601465049152 |
| 10 | 2527141116269870093700549820547891617386696704 |
| 11 | 37871241077229684530428945247828504758290562881908101848856901884765190234112 |
[1,1,1,2,6,27,2910,671418,5925456572864, 1819432729601465049152, 2527141116269870093700549820547891617386696704, 37871241077229684530428945247828504758290562881908\ 101848856901884765190234112] |