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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 7 |
| 2 | 77 |
| 3 | 777 |
| 4 | 7777 |
| 5 | 77777 |
| 6 | 777777 |
| 7 | 7777777 |
| 8 | 77777777 |
| 9 | 777777777 |
| 10 | 7777777777 |
| 11 | 77777777777 |
| 12 | 777777777777 |
| 13 | 7777777777777 |
| 14 | 77777777777777 |
| 15 | 777777777777777 |
| 16 | 7777777777777777 |
| 17 | 77777777777777777 |
| 18 | 777777777777777777 |
| 19 | 7777777777777777777 |
| 20 | 77777777777777777777 |
| 21 | 777777777777777777777 |
[0,7,77,777,7777,77777,777777,7777777,77777777, 777777777,7777777777,77777777777,777777777777, 7777777777777,77777777777777,777777777777777, 7777777777777777,77777777777777777, 777777777777777777,7777777777777777777, 77777777777777777777,777777777777777777777] |