The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 1 |
| 5 | 0 |
| 6 | 2 |
| 7 | 1 |
| 8 | 9 |
| 9 | 5 |
| 10 | 36 |
| 11 | 42 |
| 12 | 313 |
| 13 | 685 |
| 14 | 3999 |
| 15 | 16535 |
| 16 | 100897 |
| 17 | 577324 |
| 18 | 3886229 |
| 19 | 26982310 |
[0,0,0,1,0,2,1,9,5,36,42,313,685,3999,16535, 100897,577324,3886229,26982310] |