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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 18 |
| 4 | 160 |
| 5 | 2325 |
| 6 | 41895 |
| 7 | 961772 |
| 8 | 26978400 |
| 9 | 929587995 |
| 10 | 36843728625 |
| 11 | 1705290814194 |
| 12 | 89802671542272 |
| 13 | 5336424046419557 |
| 14 | 354379732734283200 |
| 15 | 26173529641406219400 |
[1,1,3,18,160,2325,41895,961772,26978400, 929587995,36843728625,1705290814194, 89802671542272,5336424046419557, 354379732734283200,26173529641406219400] |