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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 8 |
| 3 | 48 |
| 4 | 504 |
| 5 | 4680 |
| 6 | 66240 |
| 7 | 856800 |
| 8 | 14515200 |
| 9 | 242040960 |
| 10 | 4775500800 |
| 11 | 95520902400 |
| 12 | 2175146265600 |
| 13 | 50438868480000 |
| 14 | 1292330988748800 |
| 15 | 34092378448128000 |
| 16 | 971277752180736000 |
| 17 | 28566680100102144000 |
| 18 | 896191466580393984000 |
| 19 | 29029508406664077312000 |
[1,1,8,48,504,4680,66240,856800,14515200, 242040960,4775500800,95520902400,2175146265600, 50438868480000,1292330988748800,34092378448128000, 971277752180736000,28566680100102144000, 896191466580393984000,29029508406664077312000] |