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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 78 |
| 4 | 8112 |
| 5 | 81160560 |
| 6 | 8116056486963360 |
| 7 | 81160564869633656812395408743520 |
| 8 | 8116056486963365681239540874352649284518957069254499163269948160 |
[1,2,6,78,8112,81160560,8116056486963360, 81160564869633656812395408743520, 81160564869633656812395408743526492845189570692544\ 99163269948160] |