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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 9 |
| 5 | 23 |
| 6 | 57 |
| 7 | 151 |
| 8 | 427 |
| 9 | 1263 |
| 10 | 3807 |
| 11 | 11549 |
| 12 | 34843 |
| 13 | 104459 |
| 14 | 311317 |
| 15 | 928719 |
| 16 | 2776247 |
| 17 | 8320757 |
| 18 | 24967341 |
| 19 | 74985337 |
[1,1,2,4,9,23,57,151,427,1263,3807,11549,34843, 104459,311317,928719,2776247,8320757,24967341, 74985337] |