The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 2 |
| 3 | 3 |
| 4 | 8 |
| 5 | 26 |
| 6 | 108 |
| 7 | 661 |
| 8 | 6150 |
| 9 | 97585 |
| 10 | 2700050 |
| 11 | 135841840 |
| 12 | 12568984762 |
| 13 | 2179513027405 |
[0,2,3,8,26,108,661,6150,97585,2700050,135841840, 12568984762,2179513027405] |