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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | -1 |
| 2 | 2 |
| 3 | 5 |
| 4 | 19 |
| 5 | 75 |
| 6 | 305 |
| 7 | 1270 |
| 8 | 5390 |
| 9 | 23236 |
| 10 | 101480 |
| 11 | 448085 |
| 12 | 1997115 |
| 13 | 8973255 |
| 14 | 40602093 |
| 15 | 184853055 |
| 16 | 846206025 |
| 17 | 3892585325 |
| 18 | 17984308775 |
| 19 | 83417287855 |
| 20 | 388297304825 |
| 21 | 1813341109825 |
| 22 | 8493372326675 |
| 23 | 39889629750600 |
| 24 | 187812852106636 |
[1,-1,2,5,19,75,305,1270,5390,23236,101480,448085, 1997115,8973255,40602093,184853055,846206025, 3892585325,17984308775,83417287855,388297304825, 1813341109825,8493372326675,39889629750600, 187812852106636] |