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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 4 |
| 3 | 63 |
| 4 | 196 |
| 5 | 15125 |
| 6 | 838566 |
| 7 | 807905287 |
| 8 | 19896463928 |
| 9 | 3059220303009 |
| 10 | 3931520917431250 |
[2,4,63,196,15125,838566,807905287,19896463928, 3059220303009,3931520917431250] |