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| n | a(n) |
|---|---|
| 0 | 2 |
| 1 | 4 |
| 2 | 14 |
| 3 | 104 |
| 4 | 1882 |
| 5 | 94572 |
| 6 | 15028134 |
| 7 | 8378070864 |
| 8 | 17561539552946 |
| 9 | 144130531453121108 |
[2,4,14,104,1882,94572,15028134,8378070864, 17561539552946,144130531453121108] |