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| n | a(n) |
|---|---|
| 1 | 21 |
| 2 | 43 |
| 3 | 67 |
| 4 | 87 |
| 5 | 321 |
| 6 | 4321 |
| 7 | 4567 |
| 8 | 6789 |
| 9 | 78901 |
| 10 | 432109 |
| 11 | 9012345 |
| 12 | 67890123 |
| 13 | 109876543 |
| 14 | 123456789 |
| 15 | 6543210987 |
| 16 | 8901234567 |
[21,43,67,87,321,4321,4567,6789,78901,432109, 9012345,67890123,109876543,123456789,6543210987, 8901234567] |