The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 7 |
| 3 | 20 |
| 4 | 75 |
| 5 | 644 |
| 6 | 4604 |
| 7 | 116051 |
| 8 | 5133698 |
| 9 | 330723200 |
| 10 | 54246156735 |
[1,7,20,75,644,4604,116051,5133698,330723200, 54246156735] |