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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 6 |
| 4 | 48 |
| 5 | 360 |
| 6 | 2880 |
| 7 | 25200 |
| 8 | 241920 |
| 9 | 2540160 |
| 10 | 29030400 |
| 11 | 359251200 |
| 12 | 4790016000 |
| 13 | 68497228800 |
| 14 | 1046139494400 |
| 15 | 16999766784000 |
| 16 | 292919058432000 |
| 17 | 5335311421440000 |
| 18 | 102437979291648000 |
| 19 | 2067966706950144000 |
[0,0,0,6,48,360,2880,25200,241920,2540160, 29030400,359251200,4790016000,68497228800, 1046139494400,16999766784000,292919058432000, 5335311421440000,102437979291648000, 2067966706950144000] |