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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 36 |
| 3 | 900 |
| 4 | 37800 |
| 5 | 2381400 |
| 6 | 209563200 |
| 7 | 24518894400 |
| 8 | 3677834160000 |
| 9 | 687754987920000 |
| 10 | 156808137245760000 |
| 11 | 42808621468092480000 |
| 12 | 13784376112725778560000 |
| 13 | 5169141042272166960000000 |
| 14 | 2233068930261576126720000000 |
| 15 | 1100902982618957030472960000000 |
[1,3,36,900,37800,2381400,209563200,24518894400, 3677834160000,687754987920000,156808137245760000, 42808621468092480000,13784376112725778560000, 5169141042272166960000000, 2233068930261576126720000000, 1100902982618957030472960000000] |