The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 3 |
| 3 | 6 |
| 4 | 23 |
| 5 | 88 |
| 6 | 443 |
| 7 | 3960 |
| 8 | 38959 |
| 9 | 506642 |
| 10 | 11160832 |
| 11 | 284581172 |
| 12 | 9639057994 |
[1,2,3,6,23,88,443,3960,38959,506642,11160832, 284581172,9639057994] |