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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 9 |
| 2 | 129600 |
| 3 | 40327580160000 |
| 4 | 1311346674278439321600000000 |
| 5 | 13821139470331790817454891043295068160000000000 |
| 6 | 114180111981355345833797461507302737916551512227408406118400000000000000 |
[1,9,129600,40327580160000, 1311346674278439321600000000, 13821139470331790817454891043295068160000000000, 11418011198135534583379746150730273791655151222740\ 8406118400000000000000] |