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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 4 |
| 5 | 9 |
| 6 | 23 |
| 7 | 66 |
| 8 | 209 |
| 9 | 718 |
| 10 | 2645 |
| 11 | 10373 |
| 12 | 43090 |
| 13 | 188803 |
| 14 | 869191 |
| 15 | 4189511 |
[1,1,2,4,9,23,66,209,718,2645,10373,43090,188803, 869191,4189511] |