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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | -3 |
| 2 | 15 |
| 3 | -120 |
| 4 | 915 |
| 5 | -7086 |
| 6 | 56661 |
| 7 | -462405 |
| 8 | 3819165 |
| 9 | -31843110 |
| 10 | 267610443 |
| 11 | -2263491255 |
| 12 | 19246265025 |
| 13 | -164379723735 |
| 14 | 1409306287470 |
| 15 | -12122528944620 |
| 16 | 104575462390842 |
| 17 | -904411297029585 |
| 18 | 7839310835762475 |
| 19 | -68086561401745275 |
| 20 | 592417977205534017 |
[1,-3,15,-120,915,-7086,56661,-462405,3819165, -31843110,267610443,-2263491255,19246265025, -164379723735,1409306287470,-12122528944620, 104575462390842,-904411297029585,7839310835762475, -68086561401745275,592417977205534017] |