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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | -1 |
| 3 | 5 |
| 4 | -26 |
| 5 | 204 |
| 6 | -1434 |
| 7 | 16862 |
| 8 | -166536 |
| 9 | 2377512 |
| 10 | -29870400 |
| 11 | 558727872 |
| 12 | -8542202976 |
| 13 | 185546362416 |
| 14 | -3332732184768 |
| 15 | 82441247589360 |
| 16 | -1824937537167744 |
| 17 | 50908186083448320 |
| 18 | -1214743725939310848 |
| 19 | 38998680958184088960 |
| 20 | -1084067907183602910720 |
| 21 | 36452994894649858339584 |
[1,-1,5,-26,204,-1434,16862,-166536,2377512, -29870400,558727872,-8542202976,185546362416, -3332732184768,82441247589360,-1824937537167744, 50908186083448320,-1214743725939310848, 38998680958184088960,-1084067907183602910720, 36452994894649858339584] |