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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 2 |
| 2 | -1 |
| 3 | -15 |
| 4 | 42 |
| 5 | 405 |
| 6 | -2970 |
| 7 | -20475 |
| 8 | 335160 |
| 9 | 1357965 |
| 10 | -54999000 |
| 11 | -31340925 |
| 12 | 12203314200 |
| 13 | -48569546025 |
| 14 | -3449672226000 |
| 15 | 35421501740625 |
| 16 | 1174230285228000 |
| 17 | -23134846868508375 |
| 18 | -448847662070808000 |
[0,2,-1,-15,42,405,-2970,-20475,335160,1357965, -54999000,-31340925,12203314200,-48569546025, -3449672226000,35421501740625,1174230285228000, -23134846868508375,-448847662070808000] |