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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 0 |
| 3 | 0 |
| 4 | 1 |
| 5 | 0 |
| 6 | 4 |
| 7 | 8 |
| 8 | 36 |
| 9 | 105 |
| 10 | 384 |
| 11 | 1340 |
| 12 | 4975 |
| 13 | 17676 |
| 14 | 69052 |
| 15 | 270716 |
| 16 | 1093218 |
| 17 | 4455047 |
| 18 | 18246018 |
[1,0,0,1,0,4,8,36,105,384,1340,4975,17676,69052, 270716,1093218,4455047,18246018] |