The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 19 |
| 5 | 74 |
| 6 | 353 |
| 7 | 2080 |
| 8 | 16023 |
| 9 | 159526 |
| 10 | 2093244 |
| 11 | 36265070 |
| 12 | 836395102 |
| 13 | 25794670618 |
[1,1,2,6,19,74,353,2080,16023,159526,2093244, 36265070,836395102,25794670618] |