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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 2 |
| 2 | 8 |
| 3 | 336 |
| 4 | 15616 |
| 5 | 1450240 |
| 6 | 185032704 |
| 7 | 33566984192 |
| 8 | 7971973332992 |
| 9 | 2424984197529600 |
| 10 | 915532582868746240 |
| 11 | 420569934453637906432 |
| 12 | 230845747512083447021568 |
| 13 | 149228982402223336708898816 |
[0,2,8,336,15616,1450240,185032704,33566984192, 7971973332992,2424984197529600,915532582868746240, 420569934453637906432,230845747512083447021568, 149228982402223336708898816] |