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| n | a(n) |
|---|---|
| 1 | 3 |
| 2 | 7 |
| 3 | 47 |
| 4 | 4447 |
| 5 | 4444444447 |
| 6 | 44444444444444444447 |
| 7 | 44444444444444444444444447 |
[3,7,47,4447,4444444447,44444444444444444447, 44444444444444444444444447] |