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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 31 |
| 3 | 3408 |
| 4 | 873580 |
| 5 | 405071029 |
| 6 | 295716738515 |
| 7 | 312086923732368 |
| 8 | 449317984129326216 |
| 9 | 846136323944158864793 |
| 10 | 2018612200059553898143707 |
| 11 | 5949463230586042065279268128 |
| 12 | 21227845340442717633531647231668 |
| 13 | 90172805592203250075964230466892813 |
[0,1,31,3408,873580,405071029,295716738515, 312086923732368,449317984129326216, 846136323944158864793,2018612200059553898143707, 5949463230586042065279268128, 21227845340442717633531647231668, 90172805592203250075964230466892813] |