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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 0 |
| 5 | -52 |
| 6 | -440 |
| 7 | -968 |
| 8 | 20160 |
| 9 | 407248 |
| 10 | 3393568 |
| 11 | -7743232 |
| 12 | -873283840 |
| 13 | -15700243392 |
| 14 | -92423547008 |
| 15 | 3404251259008 |
| 16 | 126748437358592 |
| 17 | 1959254285705472 |
| 18 | -9945595116842496 |
| 19 | -1499843474292945920 |
[0,1,2,4,0,-52,-440,-968,20160,407248,3393568, -7743232,-873283840,-15700243392,-92423547008, 3404251259008,126748437358592,1959254285705472, -9945595116842496,-1499843474292945920] |