The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 18 |
| 5 | 285 |
| 6 | 4680 |
| 7 | 82845 |
| 8 | 1595790 |
| 9 | 33453945 |
| 10 | 760970700 |
| 11 | 18705542625 |
| 12 | 494764058250 |
| 13 | 14023390706325 |
| 14 | 424278354099600 |
| 15 | 13653335491921125 |
| 16 | 465794724725079750 |
| 17 | 16796514560465264625 |
| 18 | 638448710154151396500 |
[0,0,1,18,285,4680,82845,1595790,33453945, 760970700,18705542625,494764058250,14023390706325, 424278354099600,13653335491921125, 465794724725079750,16796514560465264625, 638448710154151396500] |