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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 9 |
| 3 | 72 |
| 4 | 900 |
| 5 | 16200 |
| 6 | 396900 |
| 7 | 12700800 |
| 8 | 514382400 |
| 9 | 25719120000 |
| 10 | 1556006760000 |
| 11 | 112032486720000 |
| 12 | 9466745127840000 |
| 13 | 927741022528320000 |
| 14 | 104370865034436000000 |
| 15 | 13359470724407808000000 |
| 16 | 1930443519676928256000000 |
| 17 | 312731850187662377472000000 |
[1,2,9,72,900,16200,396900,12700800,514382400, 25719120000,1556006760000,112032486720000, 9466745127840000,927741022528320000, 104370865034436000000,13359470724407808000000, 1930443519676928256000000, 312731850187662377472000000] |