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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 0 |
| 3 | 30 |
| 4 | 840 |
| 5 | 2730 |
| 6 | 72930 |
| 7 | 870870 |
| 8 | 9699690 |
| 9 | 340510170 |
| 10 | 9592993410 |
| 11 | 265257422430 |
| 12 | 8624101075590 |
| 13 | 304250263527210 |
| 14 | 14299762385778870 |
| 15 | 1164365758518632670 |
| 16 | 43657174563782890110 |
| 17 | 1987938667108592728530 |
| 18 | 172494415819766906755890 |
[2,0,30,840,2730,72930,870870,9699690,340510170, 9592993410,265257422430,8624101075590, 304250263527210,14299762385778870, 1164365758518632670,43657174563782890110, 1987938667108592728530,172494415819766906755890] |