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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 0 |
| 3 | 0 |
| 4 | 4 |
| 5 | -20 |
| 6 | 120 |
| 7 | -560 |
| 8 | 2784 |
| 9 | -7920 |
| 10 | -24960 |
| 11 | 1034880 |
| 12 | -14625536 |
| 13 | 172569280 |
| 14 | -1661936640 |
| 15 | 12339608320 |
| 16 | -13269651456 |
| 17 | -1902800305920 |
| 18 | 53452617646080 |
| 19 | -1037015219466240 |
| 20 | 16547577836929024 |
| 21 | -208832669083243520 |
[0,1,0,0,4,-20,120,-560,2784,-7920,-24960,1034880, -14625536,172569280,-1661936640,12339608320, -13269651456,-1902800305920,53452617646080, -1037015219466240,16547577836929024, -208832669083243520] |