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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 18 |
| 3 | 360 |
| 4 | 12600 |
| 5 | 680400 |
| 6 | 52390800 |
| 7 | 5448643200 |
| 8 | 735566832000 |
| 9 | 125046361440000 |
| 10 | 26134689540960000 |
| 11 | 6585941764321920000 |
| 12 | 1969196587532254080000 |
| 13 | 689218805636288928000000 |
| 14 | 279133616282697015840000000 |
| 15 | 129517997955171415349760000000 |
| 16 | 68255984922375335889323520000000 |
[1,2,18,360,12600,680400,52390800,5448643200, 735566832000,125046361440000,26134689540960000, 6585941764321920000,1969196587532254080000, 689218805636288928000000, 279133616282697015840000000, 129517997955171415349760000000, 68255984922375335889323520000000] |