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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 0 |
| 3 | 0 |
| 4 | 1 |
| 5 | 0 |
| 6 | 1 |
| 7 | 2 |
| 8 | 6 |
| 9 | 16 |
| 10 | 56 |
| 11 | 183 |
| 12 | 657 |
| 13 | 2277 |
| 14 | 8813 |
| 15 | 34178 |
| 16 | 137578 |
| 17 | 558734 |
| 18 | 2285694 |
[1,0,0,1,0,1,2,6,16,56,183,657,2277,8813,34178, 137578,558734,2285694] |