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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 1 |
| 5 | 3 |
| 6 | 2 |
| 7 | 9 |
| 8 | 26 |
| 9 | 79 |
| 10 | 860 |
| 11 | 1039 |
| 12 | 15799 |
| 13 | 24210 |
| 14 | 222885 |
| 15 | 480909 |
| 16 | 2649008 |
| 17 | 7803307 |
| 18 | 27963791 |
| 19 | 106837398 |
| 20 | 276117812 |
[1,1,2,1,3,2,9,26,79,860,1039,15799,24210,222885, 480909,2649008,7803307,27963791,106837398, 276117812] |