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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 8 |
| 3 | 66 |
| 4 | 864 |
| 5 | 15240 |
| 6 | 333360 |
| 7 | 8653680 |
| 8 | 259499520 |
| 9 | 8821975680 |
| 10 | 335224915200 |
| 11 | 14079333945600 |
| 12 | 647648004326400 |
| 13 | 32382382493260800 |
| 14 | 1748648405555251200 |
| 15 | 101421603773538048000 |
| 16 | 6288139373806338048000 |
| 17 | 415017197646001606656000 |
| 18 | 29051203816724366204928000 |
[2,8,66,864,15240,333360,8653680,259499520, 8821975680,335224915200,14079333945600, 647648004326400,32382382493260800, 1748648405555251200,101421603773538048000, 6288139373806338048000,415017197646001606656000, 29051203816724366204928000] |