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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 3 |
| 3 | 12 |
| 4 | 78 |
| 5 | 708 |
| 6 | 8256 |
| 7 | 117624 |
| 8 | 1980096 |
| 9 | 38456736 |
| 10 | 846413472 |
| 11 | 20819693568 |
| 12 | 565998548352 |
| 13 | 16852047061632 |
| 14 | 545372109629184 |
| 15 | 19061178127458816 |
| 16 | 715541912895773184 |
| 17 | 28713061759257037824 |
| 18 | 1226513716981332031488 |
[0,1,3,12,78,708,8256,117624,1980096,38456736, 846413472,20819693568,565998548352,16852047061632, 545372109629184,19061178127458816, 715541912895773184,28713061759257037824, 1226513716981332031488] |