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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | -2 |
| 3 | -4 |
| 4 | 20 |
| 5 | 64 |
| 6 | -488 |
| 7 | -2176 |
| 8 | 22160 |
| 9 | 126976 |
| 10 | -1616672 |
| 11 | -11321344 |
| 12 | 172976960 |
| 13 | 1431568384 |
| 14 | -25518205568 |
| 15 | -243680935936 |
| 16 | 4964227109120 |
| 17 | 53725527801856 |
| 18 | -1231298393825792 |
| 19 | -14893509177769984 |
| 20 | 379260096755225600 |
| 21 | 5070334006399074304 |
| 22 | -142026494757146421248 |
[1,1,-2,-4,20,64,-488,-2176,22160,126976,-1616672, -11321344,172976960,1431568384,-25518205568, -243680935936,4964227109120,53725527801856, -1231298393825792,-14893509177769984, 379260096755225600,5070334006399074304, -142026494757146421248] |