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| n | a(n) |
|---|---|
| 2 | 0 |
| 3 | 6 |
| 4 | 240 |
| 5 | 95520 |
| 6 | 512386560 |
| 7 | 46817046743040 |
| 8 | 87639428459458068480 |
[0,6,240,95520,512386560,46817046743040, 87639428459458068480] |