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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 6 |
| 3 | 9 |
| 4 | 10 |
| 5 | 21 |
| 6 | 65 |
| 7 | 87 |
| 8 | 321 |
| 9 | 543 |
| 10 | 4321 |
| 11 | 8765 |
| 12 | 98765 |
| 13 | 654321 |
| 14 | 876543 |
| 15 | 7654321 |
[4,6,9,10,21,65,87,321,543,4321,8765,98765,654321, 876543,7654321] |