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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | -2 |
| 3 | -2 |
| 4 | 8 |
| 5 | -24 |
| 6 | 224 |
| 7 | -720 |
| 8 | -1408 |
| 9 | 0 |
| 10 | 717824 |
| 11 | -3628800 |
| 12 | -47546368 |
| 13 | -479001600 |
| 14 | 12431673344 |
| 15 | 87178291200 |
| 16 | -68669145088 |
| 17 | -20922789888000 |
| 18 | 47215125069824 |
| 19 | -6402373705728000 |
| 20 | -159504062197792768 |
| 21 | 2432902008176640000 |
| 22 | 102176932845365755904 |
| 23 | -1124000727777607680000 |
[1,-2,-2,8,-24,224,-720,-1408,0,717824,-3628800, -47546368,-479001600,12431673344,87178291200, -68669145088,-20922789888000,47215125069824, -6402373705728000,-159504062197792768, 2432902008176640000,102176932845365755904, -1124000727777607680000] |