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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | -4 |
| 3 | 32 |
| 4 | -240 |
| 5 | 2064 |
| 6 | -18816 |
| 7 | 179264 |
| 8 | -1762816 |
| 9 | 17758976 |
| 10 | -182342400 |
| 11 | 1901196288 |
| 12 | -20075427840 |
| 13 | 214246524928 |
| 14 | -2307200135168 |
| 15 | 25039992254464 |
| 16 | -273603550461952 |
| 17 | 3007387399258112 |
| 18 | -33230774508716032 |
| 19 | 368915340555517952 |
| 20 | -4112806343370539008 |
[1,2,-4,32,-240,2064,-18816,179264,-1762816, 17758976,-182342400,1901196288,-20075427840, 214246524928,-2307200135168,25039992254464, -273603550461952,3007387399258112, -33230774508716032,368915340555517952, -4112806343370539008] |