The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 8 |
| 4 | 50 |
| 5 | 280 |
| 6 | 1475 |
| 7 | 7472 |
| 8 | 36836 |
| 9 | 178000 |
| 10 | 847045 |
| 11 | 3982200 |
| 12 | 18538134 |
| 13 | 85599912 |
| 14 | 392560775 |
| 15 | 1789800160 |
| 16 | 8119213000 |
| 17 | 36670415648 |
| 18 | 164983381129 |
| 19 | 739737725800 |
| 20 | 3306651932410 |
| 21 | 14740349833400 |
| 22 | 65546786425931 |
| 23 | 290816440554768 |
| 24 | 1287647063875500 |
| 25 | 5690631701996400 |
[0,0,1,8,50,280,1475,7472,36836,178000,847045, 3982200,18538134,85599912,392560775,1789800160, 8119213000,36670415648,164983381129,739737725800, 3306651932410,14740349833400,65546786425931, 290816440554768,1287647063875500,5690631701996400] |