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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 12 |
| 3 | 124 |
| 4 | 1245 |
| 5 | 12456 |
| 6 | 124567 |
| 7 | 1245678 |
| 8 | 12456789 |
| 9 | 1245678910 |
| 10 | 124567891011 |
| 11 | 12456789101112 |
| 12 | 1245678910111213 |
| 13 | 124567891011121314 |
| 14 | 12456789101112131415 |
| 15 | 1245678910111213141516 |
| 16 | 124567891011121314151617 |
| 17 | 12456789101112131415161718 |
| 18 | 1245678910111213141516171819 |
| 19 | 124567891011121314151617181920 |
[1,12,124,1245,12456,124567,1245678,12456789, 1245678910,124567891011,12456789101112, 1245678910111213,124567891011121314, 12456789101112131415,1245678910111213141516, 124567891011121314151617, 12456789101112131415161718, 1245678910111213141516171819, 124567891011121314151617181920] |