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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 0 |
| 3 | -10 |
| 4 | -80 |
| 5 | 0 |
| 6 | 17600 |
| 7 | 418000 |
| 8 | 0 |
| 9 | -496672000 |
| 10 | -23576960000 |
| 11 | 0 |
| 12 | 91442700800000 |
| 13 | 7255463564800000 |
| 14 | 0 |
| 15 | -69994087116448000000 |
| 16 | -8354181454767104000000 |
| 17 | 0 |
| 18 | 169165728883243642880000000 |
| 19 | 28336045031124313753600000000 |
| 20 | 0 |
| 21 | -1072156342430107319243161600000000 |
[1,1,0,-10,-80,0,17600,418000,0,-496672000, -23576960000,0,91442700800000,7255463564800000,0, -69994087116448000000,-8354181454767104000000,0, 169165728883243642880000000, 28336045031124313753600000000,0, -1072156342430107319243161600000000] |