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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 6 |
| 4 | 0 |
| 5 | 60 |
| 6 | 720 |
| 7 | 840 |
| 8 | 40320 |
| 9 | 378000 |
| 10 | 2116800 |
| 11 | 60207840 |
| 12 | 598752000 |
| 13 | 7792424640 |
| 14 | 181863601920 |
| 15 | 2288689603200 |
| 16 | 45855781171200 |
| 17 | 1016682053587200 |
| 18 | 17113328962329600 |
| 19 | 422970486434496000 |
| 20 | 9765438564930048000 |
| 21 | 213305542403822668800 |
| 22 | 5916931500898517299200 |
[1,0,0,6,0,60,720,840,40320,378000,2116800, 60207840,598752000,7792424640,181863601920, 2288689603200,45855781171200,1016682053587200, 17113328962329600,422970486434496000, 9765438564930048000,213305542403822668800, 5916931500898517299200] |