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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 0 |
| 3 | -6 |
| 4 | -36 |
| 5 | -120 |
| 6 | 240 |
| 7 | 8400 |
| 8 | 82320 |
| 9 | 362880 |
| 10 | -3507840 |
| 11 | -103783680 |
| 12 | -1268688960 |
| 13 | -4843238400 |
| 14 | 175429013760 |
| 15 | 5052189542400 |
| 16 | 68016191443200 |
| 17 | 55329155481600 |
| 18 | -23284682272051200 |
| 19 | -668640423164313600 |
| 20 | -9013925405784499200 |
| 21 | 57340797108269875200 |
[1,1,0,-6,-36,-120,240,8400,82320,362880,-3507840, -103783680,-1268688960,-4843238400,175429013760, 5052189542400,68016191443200,55329155481600, -23284682272051200,-668640423164313600, -9013925405784499200,57340797108269875200] |