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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 9 |
| 2 | 99 |
| 3 | 990 |
| 4 | 9990 |
| 5 | 99891 |
| 6 | 999900 |
| 7 | 9998901 |
| 8 | 99998910 |
| 9 | 999989010 |
| 10 | 9999989010 |
| 11 | 99999889110 |
| 12 | 999999890109 |
| 13 | 9999998890200 |
| 14 | 99999998891100 |
| 15 | 999999988901199 |
| 16 | 9999999988902090 |
| 17 | 99999999888912090 |
| 18 | 999999999889011990 |
| 19 | 9999999998889021990 |
[1,9,99,990,9990,99891,999900,9998901,99998910, 999989010,9999989010,99999889110,999999890109, 9999998890200,99999998891100,999999988901199, 9999999988902090,99999999888912090, 999999999889011990,9999999998889021990] |