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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 15 |
| 3 | 180 |
| 4 | 2100 |
| 5 | 25200 |
| 6 | 317520 |
| 7 | 4233600 |
| 8 | 59875200 |
| 9 | 898128000 |
| 10 | 14270256000 |
| 11 | 239740300800 |
| 12 | 4249941696000 |
| 13 | 79332244992000 |
| 14 | 1556132497920000 |
| 15 | 32011868528640000 |
| 16 | 689322235650048000 |
| 17 | 15509750302126080000 |
| 18 | 364022962973429760000 |
| 19 | 8898339094906060800000 |
[1,15,180,2100,25200,317520,4233600,59875200, 898128000,14270256000,239740300800,4249941696000, 79332244992000,1556132497920000,32011868528640000, 689322235650048000,15509750302126080000, 364022962973429760000,8898339094906060800000] |