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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 9 |
| 3 | 99 |
| 4 | 990 |
| 5 | 9999 |
| 6 | 99891 |
| 7 | 999999 |
| 8 | 9999000 |
| 9 | 99999900 |
| 10 | 999989991 |
| 11 | 9999999999 |
| 12 | 99999899010 |
| 13 | 999999999999 |
| 14 | 9999998999991 |
| 15 | 99999999989901 |
| 16 | 999999990000000 |
| 17 | 9999999999999999 |
| 18 | 99999999899900100 |
| 19 | 999999999999999999 |
| 20 | 9999999998999999010 |
| 21 | 99999999999998999901 |
[1,9,99,990,9999,99891,999999,9999000,99999900, 999989991,9999999999,99999899010,999999999999, 9999998999991,99999999989901,999999990000000, 9999999999999999,99999999899900100, 999999999999999999,9999999998999999010, 99999999999998999901] |