| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | -4 |
| 3 | 12 |
| 4 | -120 |
| 5 | 1080 |
| 6 | -14400 |
| 7 | 241920 |
| 8 | -4233600 |
| 9 | 103783680 |
| 10 | -2408071680 |
| 11 | 74468782080 |
| 12 | -2230518850560 |
| 13 | 81262621440000 |
| 14 | -2999630643609600 |
| 15 | 125381910682828800 |
| 16 | -5464949027586048000 |
| 17 | 258986473607083622400 |
| 18 | -12924791918438400000000 |
| 19 | 688106822684149835366400 |
[1,1,-4,12,-120,1080,-14400,241920,-4233600, 103783680,-2408071680,74468782080,-2230518850560, 81262621440000,-2999630643609600, 125381910682828800,-5464949027586048000, 258986473607083622400,-12924791918438400000000, 688106822684149835366400] |