The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 1 |
| 6 | 2 |
| 7 | 9 |
| 8 | 49 |
| 9 | 455 |
| 10 | 5784 |
| 11 | 90940 |
| 12 | 1620491 |
| 13 | 31478651 |
| 14 | 656784488 |
| 15 | 14621878339 |
| 16 | 345975756388 |
[1,0,0,0,0,1,2,9,49,455,5784,90940,1620491, 31478651,656784488,14621878339,345975756388] |