| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | -9 |
| 3 | 60 |
| 4 | -360 |
| 5 | 2457 |
| 6 | -18036 |
| 7 | 138429 |
| 8 | -1093500 |
| 9 | 8833140 |
| 10 | -72622224 |
| 11 | 605563452 |
| 12 | -5108366277 |
| 13 | 43512281460 |
| 14 | -373690245420 |
| 15 | 3232056818511 |
| 16 | -28126143258444 |
| 17 | 246080268205092 |
| 18 | -2163254305208580 |
| 19 | 19097478037041840 |
| 20 | -169235311045503708 |
| 21 | 1504837859547132468 |
[1,3,-9,60,-360,2457,-18036,138429,-1093500, 8833140,-72622224,605563452,-5108366277, 43512281460,-373690245420,3232056818511, -28126143258444,246080268205092,-2163254305208580, 19097478037041840,-169235311045503708, 1504837859547132468] |