| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | -1 |
| 3 | 2 |
| 4 | -6 |
| 5 | 30 |
| 6 | -210 |
| 7 | 1890 |
| 8 | -20790 |
| 9 | 270270 |
| 10 | -4054050 |
| 11 | 68918850 |
| 12 | -1309458150 |
| 13 | 27498621150 |
| 14 | -632468286450 |
| 15 | 15811707161250 |
| 16 | -426916093353750 |
| 17 | 12380566707258750 |
| 18 | -383797567925021250 |
| 19 | 12665319741525701250 |
[1,-1,2,-6,30,-210,1890,-20790,270270,-4054050, 68918850,-1309458150,27498621150,-632468286450, 15811707161250,-426916093353750,12380566707258750, -383797567925021250,12665319741525701250] |