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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 6 |
| 4 | 24 |
| 5 | 60 |
| 6 | 1080 |
| 7 | 9240 |
| 8 | 80640 |
| 9 | 1058400 |
| 10 | 13759200 |
| 11 | 190935360 |
| 12 | 3053635200 |
| 13 | 51632380800 |
| 14 | 941283383040 |
| 15 | 18521494992000 |
| 16 | 387100672358400 |
| 17 | 8613563883724800 |
| 18 | 203100697223424000 |
| 19 | 5053907407233484800 |
| 20 | 132496193336322816000 |
| 21 | 3648203578700448768000 |
[1,0,0,6,24,60,1080,9240,80640,1058400,13759200, 190935360,3053635200,51632380800,941283383040, 18521494992000,387100672358400,8613563883724800, 203100697223424000,5053907407233484800, 132496193336322816000,3648203578700448768000] |