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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 1440 |
| 4 | 689762304000 |
| 5 | 1678124094566146045378560000000 |
| 6 | 445127215203413988036981576746329306509322538188800000000000000 |
[1,1,2,1440,689762304000, 1678124094566146045378560000000, 44512721520341398803698157674632930650932253818880\ 0000000000000] |