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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | -1 |
| 2 | -6 |
| 3 | 15 |
| 4 | 272 |
| 5 | -745 |
| 6 | -29976 |
| 7 | 61271 |
| 8 | 6065856 |
| 9 | -2723697 |
| 10 | -1941455080 |
| 11 | -3989345041 |
| 12 | 897021218400 |
| 13 | 4964061925511 |
| 14 | -562221881675832 |
| 15 | -5689641396555705 |
| 16 | 456732442022509184 |
| 17 | 7321841133968133023 |
| 18 | -464200472167634521800 |
| 19 | -10961686347887871324289 |
| 20 | 573373115861405030522400 |
[1,-1,-6,15,272,-745,-29976,61271,6065856, -2723697,-1941455080,-3989345041,897021218400, 4964061925511,-562221881675832,-5689641396555705, 456732442022509184,7321841133968133023, -464200472167634521800,-10961686347887871324289, 573373115861405030522400] |