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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 36 |
| 3 | 216 |
| 4 | 1440 |
| 5 | 9936 |
| 6 | 74880 |
| 7 | 608040 |
| 8 | 5391360 |
| 9 | 51732000 |
| 10 | 539136000 |
| 11 | 6055025400 |
| 12 | 73322496000 |
| 13 | 950831881200 |
| 14 | 13198049280000 |
| 15 | 194943875747400 |
| 16 | 3061947432960000 |
| 17 | 50884296047208000 |
| 18 | 894088650424320000 |
[1,0,36,216,1440,9936,74880,608040,5391360, 51732000,539136000,6055025400,73322496000, 950831881200,13198049280000,194943875747400, 3061947432960000,50884296047208000, 894088650424320000] |