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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | -2 |
| 3 | 3 |
| 4 | -12 |
| 5 | 15 |
| 6 | 45 |
| 7 | -105 |
| 8 | 420 |
| 9 | -1890 |
| 10 | -4725 |
| 11 | 10395 |
| 12 | 31185 |
| 13 | -135135 |
| 14 | -315315 |
| 15 | -4729725 |
| 16 | 4729725 |
| 17 | -80405325 |
| 18 | -723647925 |
| 19 | 1527701175 |
| 20 | 7638505875 |
| 21 | 53469541125 |
| 22 | 117632990475 |
| 23 | -245959889175 |
| 24 | -737879667525 |
| 25 | 18446991688125 |
| 26 | 79936963981875 |
| 27 | -2158298027510625 |
[1,-2,3,-12,15,45,-105,420,-1890,-4725,10395, 31185,-135135,-315315,-4729725,4729725,-80405325, -723647925,1527701175,7638505875,53469541125, 117632990475,-245959889175,-737879667525, 18446991688125,79936963981875,-2158298027510625] |