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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 4 |
| 5 | 14 |
| 6 | 38 |
| 7 | 216 |
| 8 | 600 |
| 9 | 6240 |
| 10 | 9552 |
| 11 | 319296 |
| 12 | -519312 |
| 13 | 28108560 |
| 14 | -176474352 |
| 15 | 3998454144 |
| 16 | -43985078784 |
| 17 | 837126163584 |
| 18 | -12437000028288 |
| 19 | 237195036797184 |
| 20 | -4235955315745536 |
| 21 | 85886259443020800 |
| 22 | -1746536474655406080 |
| 23 | 38320721602434017280 |
| 24 | -864056965711935974400 |
[1,1,1,2,4,14,38,216,600,6240,9552,319296,-519312, 28108560,-176474352,3998454144,-43985078784, 837126163584,-12437000028288,237195036797184, -4235955315745536,85886259443020800, -1746536474655406080,38320721602434017280, -864056965711935974400] |