The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 3 |
| 5 | 7 |
| 6 | 36 |
| 7 | 221 |
| 8 | 2184 |
| 9 | 26985 |
| 10 | 395877 |
| 11 | 6362861 |
| 12 | 108791383 |
[0,0,1,3,7,36,221,2184,26985,395877,6362861, 108791383] |