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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 6 |
| 4 | 0 |
| 5 | 60 |
| 6 | 1440 |
| 7 | 840 |
| 8 | 100800 |
| 9 | 1829520 |
| 10 | 6350400 |
| 11 | 419459040 |
| 12 | 7125148800 |
| 13 | 72657224640 |
| 14 | 3691516308480 |
| 15 | 66691652227200 |
| 16 | 1362335156582400 |
| 17 | 60600254383468800 |
| 18 | 1285478183493504000 |
| 19 | 40463468995171622400 |
| 20 | 1701073478756171520000 |
[1,0,0,6,0,60,1440,840,100800,1829520,6350400, 419459040,7125148800,72657224640,3691516308480, 66691652227200,1362335156582400,60600254383468800, 1285478183493504000,40463468995171622400, 1701073478756171520000] |