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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | -1 |
| 3 | 3 |
| 4 | -6 |
| 5 | 23 |
| 6 | -105 |
| 7 | 406 |
| 8 | -1260 |
| 9 | 1385 |
| 10 | 48195 |
| 11 | -816794 |
| 12 | 7746354 |
| 13 | -28590343 |
| 14 | -859023165 |
| 15 | 32103094024 |
| 16 | -771444393720 |
| 17 | 15805494180377 |
| 18 | -295855009807833 |
| 19 | 5153505812257222 |
| 20 | -82415471899841090 |
[0,0,-1,3,-6,23,-105,406,-1260,1385,48195,-816794, 7746354,-28590343,-859023165,32103094024, -771444393720,15805494180377,-295855009807833, 5153505812257222,-82415471899841090] |