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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 9 |
| 4 | 162 |
| 5 | 2250 |
| 6 | 29700 |
| 7 | 396900 |
| 8 | 5503680 |
| 9 | 80015040 |
| 10 | 1224720000 |
| 11 | 19758816000 |
| 12 | 335899872000 |
| 13 | 6010631827200 |
| 14 | 113048449113600 |
| 15 | 2231219390400000 |
| 16 | 46134751703040000 |
| 17 | 997703235809280000 |
| 18 | 22529953070456832000 |
| 19 | 530433460332711936000 |
| 20 | 13000820106193920000000 |
[0,0,9,162,2250,29700,396900,5503680,80015040, 1224720000,19758816000,335899872000,6010631827200, 113048449113600,2231219390400000, 46134751703040000,997703235809280000, 22529953070456832000,530433460332711936000, 13000820106193920000000] |