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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 4 |
| 3 | 238 |
| 4 | 31992 |
| 5 | 9390096 |
| 6 | 4755878928 |
| 7 | 3802500283680 |
| 8 | 4720879431568800 |
| 9 | 8379987002639042400 |
| 10 | 20346893722025317036800 |
[1,0,4,238,31992,9390096,4755878928,3802500283680, 4720879431568800,8379987002639042400, 20346893722025317036800] |