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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | -1 |
| 3 | 0 |
| 4 | 1 |
| 5 | 2 |
| 6 | 4 |
| 7 | 6 |
| 8 | 19 |
| 9 | 38 |
| 10 | 67 |
| 11 | 127 |
| 12 | 234 |
| 13 | 419 |
| 14 | 745 |
| 15 | 1378 |
| 16 | 2678 |
| 17 | 5311 |
| 18 | 10470 |
| 19 | 20333 |
[0,-1,0,1,2,4,6,19,38,67,127,234,419,745,1378, 2678,5311,10470,20333] |