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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 900 |
| 3 | 99000 |
| 4 | 9990000 |
| 5 | 999900000 |
| 6 | 99999000000 |
| 7 | 9999990000000 |
| 8 | 999999900000000 |
| 9 | 99999999000000000 |
| 10 | 5555555595555555550555555555 |
| 11 | 9555555559505555555505055555555 |
| 12 | 9955555555950055555555050055555555 |
| 13 | 9995555555595000555555550500055555555 |
[0,900,99000,9990000,999900000,99999000000, 9999990000000,999999900000000,99999999000000000, 5555555595555555550555555555, 9555555559505555555505055555555, 9955555555950055555555050055555555, 9995555555595000555555550500055555555] |