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| n | a(n) |
|---|---|
| 1 | 19 |
| 2 | 109 |
| 3 | 991 |
| 4 | 1009 |
| 5 | 10009 |
| 6 | 99991 |
| 7 | 9999991 |
| 8 | 1000000009 |
| 9 | 1000000000000000009 |
| 10 | 10000000000000000000009 |
| 11 | 999999999999999999999999999999991 |
| 12 | 999999999999999999999999999999999999999999991 |
[19,109,991,1009,10009,99991,9999991,1000000009, 1000000000000000009,10000000000000000000009, 999999999999999999999999999999991, 999999999999999999999999999999999999999999991] |