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| n | a(n) |
|---|---|
| 1 | 7 |
| 2 | 97 |
| 3 | 977 |
| 4 | 7877 |
| 5 | 97777 |
| 6 | 787777 |
| 7 | 7877777 |
| 8 | 77777747 |
| 9 | 787777777 |
| 10 | 8777777777 |
| 11 | 79777777777 |
| 12 | 777777779777 |
| 13 | 7877777777777 |
| 14 | 77777779777777 |
| 15 | 778777777777777 |
| 16 | 8777777777777777 |
| 17 | 77797777777777777 |
| 18 | 797777777777777777 |
| 19 | 7777877777777777777 |
| 20 | 97777777777777777777 |
[7,97,977,7877,97777,787777,7877777,77777747, 787777777,8777777777,79777777777,777777779777, 7877777777777,77777779777777,778777777777777, 8777777777777777,77797777777777777, 797777777777777777,7777877777777777777, 97777777777777777777] |