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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 3 |
| 5 | 6 |
| 6 | 16 |
| 7 | 42 |
| 8 | 115 |
| 9 | 319 |
| 10 | 909 |
| 11 | 2614 |
| 12 | 7622 |
| 13 | 22422 |
| 14 | 66556 |
| 15 | 198946 |
| 16 | 598617 |
| 17 | 1811205 |
| 18 | 5508015 |
| 19 | 16825307 |
| 20 | 51605568 |
| 21 | 158860950 |
| 22 | 490666293 |
| 23 | 1520106655 |
| 24 | 4722502437 |
| 25 | 14708971581 |
| 26 | 45921804883 |
| 27 | 143682973435 |
| 28 | 450477673623 |
[1,1,1,3,6,16,42,115,319,909,2614,7622,22422, 66556,198946,598617,1811205,5508015,16825307, 51605568,158860950,490666293,1520106655, 4722502437,14708971581,45921804883,143682973435, 450477673623] |