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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 21 |
| 3 | 421 |
| 4 | 8421 |
| 5 | 168421 |
| 6 | 3368421 |
| 7 | 67368421 |
| 8 | 1347368421 |
| 9 | 26947368421 |
| 10 | 538947368421 |
| 11 | 10778947368421 |
| 12 | 215578947368421 |
| 13 | 4311578947368421 |
| 14 | 86231578947368421 |
| 15 | 1724631578947368421 |
| 16 | 34492631578947368421 |
| 17 | 689852631578947368421 |
| 18 | 13797052631578947368421 |
| 19 | 275941052631578947368421 |
[0,1,21,421,8421,168421,3368421,67368421, 1347368421,26947368421,538947368421, 10778947368421,215578947368421,4311578947368421, 86231578947368421,1724631578947368421, 34492631578947368421,689852631578947368421, 13797052631578947368421,275941052631578947368421] |