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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | -1 |
| 3 | -2 |
| 4 | 4 |
| 5 | 20 |
| 6 | -61 |
| 7 | -296 |
| 8 | 1184 |
| 9 | 9680 |
| 10 | -49201 |
| 11 | -393120 |
| 12 | 2361844 |
| 13 | 26927680 |
| 14 | -191422141 |
| 15 | -2138039424 |
| 16 | 17147588384 |
| 17 | 250712561920 |
| 18 | -2289437638081 |
| 19 | -32881696158208 |
| 20 | 329955144475204 |
| 21 | 5885687604556800 |
| 22 | -65643617893832221 |
[0,1,-1,-2,4,20,-61,-296,1184,9680,-49201,-393120, 2361844,26927680,-191422141,-2138039424, 17147588384,250712561920,-2289437638081, -32881696158208,329955144475204,5885687604556800, -65643617893832221] |