The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | -1 |
| 3 | 3 |
| 4 | -6 |
| 5 | 15 |
| 6 | -135 |
| 7 | 1260 |
| 8 | -8820 |
| 9 | 65205 |
| 10 | -722925 |
| 11 | 9043650 |
| 12 | -101974950 |
| 13 | 1197971775 |
| 14 | -17665522875 |
| 15 | 286053768000 |
| 16 | -4408292889000 |
| 17 | 70284304715625 |
| 18 | -1307027554457625 |
| 19 | 26160675737946750 |
| 20 | -509941992726416250 |
[0,0,-1,3,-6,15,-135,1260,-8820,65205,-722925, 9043650,-101974950,1197971775,-17665522875, 286053768000,-4408292889000,70284304715625, -1307027554457625,26160675737946750, -509941992726416250] |