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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 18 |
| 3 | 168 |
| 4 | 2088 |
| 5 | 32400 |
| 6 | 603360 |
| 7 | 13109040 |
| 8 | 325503360 |
| 9 | 9092684160 |
| 10 | 282219033600 |
| 11 | 9635476435200 |
| 12 | 358879494758400 |
| 13 | 14480588157235200 |
| 14 | 629228583138355200 |
| 15 | 29295027261916416000 |
| 16 | 1454816084780298240000 |
[1,3,18,168,2088,32400,603360,13109040,325503360, 9092684160,282219033600,9635476435200, 358879494758400,14480588157235200, 629228583138355200,29295027261916416000, 1454816084780298240000] |