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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 909 |
| 2 | 99099 |
| 3 | 9990999 |
| 4 | 999909999 |
| 5 | 99999099999 |
| 6 | 9999990999999 |
| 7 | 999999909999999 |
| 8 | 99999999099999999 |
| 9 | 9999999990999999999 |
| 10 | 999999999909999999999 |
| 11 | 99999999999099999999999 |
| 12 | 9999999999990999999999999 |
| 13 | 999999999999909999999999999 |
| 14 | 99999999999999099999999999999 |
| 15 | 9999999999999990999999999999999 |
[0,909,99099,9990999,999909999,99999099999, 9999990999999,999999909999999,99999999099999999, 9999999990999999999,999999999909999999999, 99999999999099999999999,9999999999990999999999999, 999999999999909999999999999, 99999999999999099999999999999, 9999999999999990999999999999999] |