The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 0 |
| 3 | 2 |
| 4 | 6 |
| 5 | 30 |
| 6 | 180 |
| 7 | 1260 |
| 8 | 9720 |
| 9 | 83100 |
| 10 | 765456 |
| 11 | 7666722 |
| 12 | 82008890 |
| 13 | 943538544 |
| 14 | 11524375162 |
| 15 | 150143430468 |
| 16 | 2065180190206 |
| 17 | 30086424947400 |
| 18 | 460533014625124 |
[1,0,2,6,30,180,1260,9720,83100,765456,7666722, 82008890,943538544,11524375162,150143430468, 2065180190206,30086424947400,460533014625124] |