The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | -1 |
| 3 | 1 |
| 4 | -6 |
| 5 | 23 |
| 6 | -150 |
| 7 | 929 |
| 8 | -8120 |
| 9 | 73387 |
| 10 | -791280 |
| 11 | 9118019 |
| 12 | -118205208 |
| 13 | 1645324757 |
| 14 | -25017568576 |
| 15 | 407175866733 |
| 16 | -7122304020000 |
| 17 | 132554586404695 |
| 18 | -2623938745643136 |
| 19 | 54936833779465199 |
[0,0,-1,1,-6,23,-150,929,-8120,73387,-791280, 9118019,-118205208,1645324757,-25017568576, 407175866733,-7122304020000,132554586404695, -2623938745643136,54936833779465199] |