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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 9 |
| 2 | 90 |
| 3 | 99 |
| 4 | 900 |
| 5 | 909 |
| 6 | 990 |
| 7 | 999 |
| 8 | 9000 |
| 9 | 9009 |
| 10 | 9090 |
| 11 | 9099 |
| 12 | 9900 |
| 13 | 9909 |
| 14 | 9990 |
| 15 | 9999 |
| 16 | 90000 |
| 17 | 90009 |
| 18 | 90090 |
| 19 | 90099 |
| 20 | 90900 |
| 21 | 90909 |
| 22 | 90990 |
| 23 | 90999 |
| 24 | 99000 |
| 25 | 99009 |
| 26 | 99090 |
| 27 | 99099 |
| 28 | 99900 |
| 29 | 99909 |
| 30 | 99990 |
| 31 | 99999 |
| 32 | 900000 |
| 33 | 900009 |
| 34 | 900090 |
| 35 | 900099 |
| 36 | 900900 |
[0,9,90,99,900,909,990,999,9000,9009,9090,9099, 9900,9909,9990,9999,90000,90009,90090,90099,90900, 90909,90990,90999,99000,99009,99090,99099,99900, 99909,99990,99999,900000,900009,900090,900099, 900900] |