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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 12 |
| 3 | 123 |
| 4 | 1234 |
| 5 | 12345 |
| 6 | 123457 |
| 7 | 1234578 |
| 8 | 12345789 |
| 9 | 1234578910 |
| 10 | 123457891011 |
| 11 | 12345789101112 |
| 12 | 1234578910111213 |
| 13 | 123457891011121314 |
| 14 | 12345789101112131415 |
| 15 | 1234578910111213141516 |
| 16 | 123457891011121314151617 |
| 17 | 12345789101112131415161718 |
| 18 | 1234578910111213141516171819 |
| 19 | 123457891011121314151617181920 |
[1,12,123,1234,12345,123457,1234578,12345789, 1234578910,123457891011,12345789101112, 1234578910111213,123457891011121314, 12345789101112131415,1234578910111213141516, 123457891011121314151617, 12345789101112131415161718, 1234578910111213141516171819, 123457891011121314151617181920] |