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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 121 |
| 2 | 12121 |
| 3 | 12321 |
| 4 | 1212121 |
| 5 | 1212321 |
| 6 | 1232121 |
| 7 | 1232321 |
| 8 | 1234321 |
| 9 | 121212121 |
| 10 | 121212321 |
| 11 | 121232121 |
| 12 | 121232321 |
| 13 | 121234321 |
| 14 | 123212121 |
| 15 | 123212321 |
| 16 | 123232121 |
| 17 | 123232321 |
| 18 | 123234321 |
| 19 | 123432121 |
| 20 | 123432321 |
| 21 | 123434321 |
| 22 | 123454321 |
[1,121,12121,12321,1212121,1212321,1232121, 1232321,1234321,121212121,121212321,121232121, 121232321,121234321,123212121,123212321,123232121, 123232321,123234321,123432121,123432321,123434321, 123454321] |