The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 5 |
| 3 | 20 |
| 4 | 149 |
| 5 | 1852 |
| 6 | 34354 |
| 7 | 873386 |
| 8 | 28671789 |
| 9 | 1166062774 |
| 10 | 56973937168 |
| 11 | 3266313635225 |
| 12 | 215667757729237 |
[2,5,20,149,1852,34354,873386,28671789,1166062774, 56973937168,3266313635225,215667757729237] |