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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 12 |
| 3 | 123 |
| 4 | 1234 |
| 5 | 12345 |
| 6 | 123456 |
| 7 | 1234567 |
| 8 | 12345678 |
| 9 | 1234567810 |
| 10 | 123456781011 |
| 11 | 12345678101112 |
| 12 | 1234567810111213 |
| 13 | 123456781011121314 |
| 14 | 12345678101112131415 |
| 15 | 1234567810111213141516 |
| 16 | 123456781011121314151617 |
| 17 | 12345678101112131415161718 |
| 18 | 1234567810111213141516171819 |
| 19 | 123456781011121314151617181920 |
[1,12,123,1234,12345,123456,1234567,12345678, 1234567810,123456781011,12345678101112, 1234567810111213,123456781011121314, 12345678101112131415,1234567810111213141516, 123456781011121314151617, 12345678101112131415161718, 1234567810111213141516171819, 123456781011121314151617181920] |