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| n | a(n) |
|---|---|
| 1 | 77767777 |
| 2 | 77777177 |
| 3 | 77777377 |
| 4 | 77777747 |
| 5 | 137777777 |
| 6 | 172777777 |
| 7 | 177677777 |
| 8 | 177776777 |
| 9 | 177777377 |
| 10 | 177777577 |
| 11 | 177777727 |
| 12 | 177777773 |
| 13 | 177777779 |
| 14 | 177797777 |
| 15 | 197777777 |
| 16 | 272777777 |
| 17 | 277177777 |
| 18 | 277727777 |
| 19 | 277771777 |
| 20 | 277775777 |
| 21 | 277777177 |
[77767777,77777177,77777377,77777747,137777777, 172777777,177677777,177776777,177777377,177777577, 177777727,177777773,177777779,177797777,197777777, 272777777,277177777,277727777,277771777,277775777, 277777177] |