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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 6 |
| 4 | 48 |
| 5 | 120 |
| 6 | 1440 |
| 7 | 25200 |
| 8 | 282240 |
| 9 | 2903040 |
| 10 | 50803200 |
| 11 | 958003200 |
| 12 | 16286054400 |
| 13 | 305124019200 |
| 14 | 6887085004800 |
| 15 | 160843947264000 |
| 16 | 3807947759616000 |
| 17 | 98169730154496000 |
| 18 | 2746618319757312000 |
[1,0,0,6,48,120,1440,25200,282240,2903040, 50803200,958003200,16286054400,305124019200, 6887085004800,160843947264000,3807947759616000, 98169730154496000,2746618319757312000] |