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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 3 |
| 4 | 4 |
| 5 | 9 |
| 6 | 21 |
| 7 | 91 |
| 8 | 1517 |
| 9 | 385318 |
| 10 | 24745571498 |
| 11 | 102057218155974827415 |
| 12 | 1735945962956039658808082636319818286550 |
[1,2,3,4,9,21,91,1517,385318,24745571498, 102057218155974827415, 1735945962956039658808082636319818286550] |