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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | -9 |
| 4 | 60 |
| 5 | -390 |
| 6 | 2820 |
| 7 | -24010 |
| 8 | 238336 |
| 9 | -2659104 |
| 10 | 32417160 |
| 11 | -426027008 |
| 12 | 6004088112 |
| 13 | -90491148176 |
| 14 | 1454386367616 |
| 15 | -24843370627920 |
| 16 | 449435283828992 |
| 17 | -8582294948325760 |
| 18 | 172476215457600000 |
| 19 | -3638420414864043264 |
[1,0,1,-9,60,-390,2820,-24010,238336,-2659104, 32417160,-426027008,6004088112,-90491148176, 1454386367616,-24843370627920,449435283828992, -8582294948325760,172476215457600000, -3638420414864043264] |