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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 4 |
| 5 | 7 |
| 6 | 13 |
| 7 | 27 |
| 8 | 55 |
| 9 | 125 |
| 10 | 278 |
| 11 | 650 |
| 12 | 1510 |
| 13 | 3624 |
| 14 | 8655 |
| 15 | 21017 |
| 16 | 51212 |
| 17 | 125857 |
| 18 | 310581 |
| 19 | 770767 |
| 20 | 1920226 |
[1,1,2,4,7,13,27,55,125,278,650,1510,3624,8655, 21017,51212,125857,310581,770767,1920226] |