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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 66 |
| 3 | 1197 |
| 4 | 21551 |
| 5 | 388159 |
| 6 | 6991108 |
| 7 | 125915577 |
| 8 | 2267843221 |
| 9 | 40845722318 |
| 10 | 735665065835 |
[4,66,1197,21551,388159,6991108,125915577, 2267843221,40845722318,735665065835] |