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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 9 |
| 5 | 20 |
| 6 | 44 |
| 7 | 74 |
| 8 | 123 |
| 9 | 231 |
| 10 | 441 |
| 11 | 681 |
| 12 | 1188 |
| 13 | 1889 |
| 14 | 3110 |
| 15 | 5448 |
| 16 | 8310 |
| 17 | 13046 |
[1,1,2,6,9,20,44,74,123,231,441,681,1188,1889, 3110,5448,8310,13046] |