The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 2 |
| 4 | 9 |
| 5 | 44 |
| 6 | 245 |
| 7 | 1462 |
| 8 | 9157 |
| 9 | 59368 |
| 10 | 395033 |
| 11 | 2682282 |
| 12 | 18510561 |
| 13 | 129451492 |
| 14 | 915401757 |
| 15 | 6534282398 |
| 16 | 47020440413 |
| 17 | 340733200288 |
| 18 | 2484299720065 |
| 19 | 18211441554706 |
| 20 | 134145473550009 |
| 21 | 992385470273692 |
| 22 | 7370066147881413 |
[1,0,1,2,9,44,245,1462,9157,59368,395033,2682282, 18510561,129451492,915401757,6534282398, 47020440413,340733200288,2484299720065, 18211441554706,134145473550009,992385470273692, 7370066147881413] |