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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 5 |
| 3 | 15 |
| 4 | 49 |
| 5 | 140 |
| 6 | -64 |
| 7 | -8540 |
| 8 | -146124 |
| 9 | -2124936 |
| 10 | -30374136 |
| 11 | -445116672 |
| 12 | -6793958016 |
| 13 | -108691150464 |
| 14 | -1826654613120 |
| 15 | -32257962443520 |
| 16 | -598196854045440 |
| 17 | -11635261535301120 |
| 18 | -237044583523514880 |
| 19 | -5050811716879104000 |
[1,2,5,15,49,140,-64,-8540,-146124,-2124936, -30374136,-445116672,-6793958016,-108691150464, -1826654613120,-32257962443520,-598196854045440, -11635261535301120,-237044583523514880, -5050811716879104000] |