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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 18 |
| 3 | 952 |
| 4 | 60878 |
| 5 | 4319328 |
| 6 | 325354277 |
| 7 | 25539764546 |
| 8 | 2066227060325 |
[1,18,952,60878,4319328,325354277,25539764546, 2066227060325] |