The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 8 |
| 4 | 68 |
| 5 | 550 |
| 6 | 5404 |
| 7 | 54768 |
| 8 | 581868 |
| 9 | 6329407 |
| 10 | 70335294 |
| 11 | 794064734 |
| 12 | 9083306888 |
| 13 | 105021662154 |
[1,2,8,68,550,5404,54768,581868,6329407,70335294, 794064734,9083306888,105021662154] |