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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 3 |
| 4 | 9 |
| 5 | 58 |
| 6 | 160 |
| 7 | 440 |
| 8 | 1166 |
| 9 | 3202 |
| 10 | 8656 |
| 11 | 23475 |
| 12 | 64194 |
| 13 | 174557 |
| 14 | 473592 |
| 15 | 1286383 |
| 16 | 3495241 |
| 17 | 9501807 |
| 18 | 25833916 |
[0,0,3,9,58,160,440,1166,3202,8656,23475,64194, 174557,473592,1286383,3495241,9501807,25833916] |