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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 3 |
| 3 | 9 |
| 4 | 29 |
| 5 | 90 |
| 6 | 285 |
| 7 | 886 |
| 8 | 2764 |
| 9 | 8543 |
| 10 | 26387 |
| 11 | 81091 |
| 12 | 248752 |
| 13 | 760687 |
| 14 | 2321950 |
| 15 | 7072376 |
[0,1,3,9,29,90,285,886,2764,8543,26387,81091, 248752,760687,2321950,7072376] |