The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 2 |
| 4 | 9 |
| 5 | 36 |
| 6 | 170 |
| 7 | 832 |
| 8 | 4318 |
| 9 | 23164 |
| 10 | 128141 |
| 11 | 725806 |
| 12 | 4194923 |
| 13 | 24657628 |
| 14 | 147053105 |
| 15 | 888044678 |
| 16 | 5421873743 |
| 17 | 33423442196 |
| 18 | 207811667858 |
| 19 | 1301996110320 |
| 20 | 8213617403274 |
| 21 | 52138266933540 |
| 22 | 332834181990220 |
[0,1,2,9,36,170,832,4318,23164,128141,725806, 4194923,24657628,147053105,888044678,5421873743, 33423442196,207811667858,1301996110320, 8213617403274,52138266933540,332834181990220] |