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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 2 |
| 3 | 120 |
| 4 | 121 |
| 5 | 201 |
| 6 | 2120 |
| 7 | 12120 |
| 8 | 121201 |
| 9 | 212012 |
| 10 | 12012120 |
| 11 | 12120121 |
| 12 | 20121201 |
| 13 | 212012120 |
| 14 | 1212012120 |
| 15 | 12120121201 |
| 16 | 21201212012 |
| 17 | 1201212012120 |
| 18 | 1212012120121 |
| 19 | 2012120121201 |
| 20 | 21201212012120 |
| 21 | 121201212012120 |
[0,1,2,120,121,201,2120,12120,121201,212012, 12012120,12120121,20121201,212012120,1212012120, 12120121201,21201212012,1201212012120, 1212012120121,2012120121201,21201212012120, 121201212012120] |