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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 20 |
| 4 | 107 |
| 5 | 577 |
| 6 | 3010 |
| 7 | 14429 |
| 8 | 56640 |
| 9 | 98020 |
| 10 | -1297568 |
| 11 | -21901213 |
| 12 | -232421636 |
| 13 | -2081040375 |
| 14 | -16862259358 |
| 15 | -126674303915 |
| 16 | -887771735205 |
| 17 | -5768588276072 |
| 18 | -33971373570320 |
| 19 | -170393703586467 |
| 20 | -576946353425125 |
| 21 | 1101490168511323 |
| 22 | 47657979846612682 |
[1,1,4,20,107,577,3010,14429,56640,98020,-1297568, -21901213,-232421636,-2081040375,-16862259358, -126674303915,-887771735205,-5768588276072, -33971373570320,-170393703586467,-576946353425125, 1101490168511323,47657979846612682] |