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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 24 |
| 3 | 208 |
| 4 | 2208 |
| 5 | 28864 |
| 6 | 440064 |
| 7 | 7752448 |
| 8 | 153604608 |
| 9 | 3398247424 |
| 10 | 82812002304 |
| 11 | 2208100261888 |
| 12 | 63835179614208 |
| 13 | 1991789102301184 |
| 14 | 66630050985836544 |
[1,4,24,208,2208,28864,440064,7752448,153604608, 3398247424,82812002304,2208100261888, 63835179614208,1991789102301184,66630050985836544] |