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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 4 |
| 3 | 27 |
| 4 | 704 |
| 5 | 26250 |
| 6 | 1573344 |
| 7 | 137145120 |
| 8 | 16494166016 |
| 9 | 2622125642472 |
| 10 | 532936224000000 |
| 11 | 134858889573071400 |
| 12 | 41584752648545107968 |
| 13 | 15351240982641183631440 |
| 14 | 6684412762278362097401856 |
| 15 | 3390180844777789569609375000 |
| 16 | 1981175610959755697378851553280 |
[1,0,4,27,704,26250,1573344,137145120,16494166016, 2622125642472,532936224000000,134858889573071400, 41584752648545107968,15351240982641183631440, 6684412762278362097401856, 3390180844777789569609375000, 1981175610959755697378851553280] |