The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 8 |
| 3 | 42 |
| 4 | 268 |
| 5 | 1994 |
| 6 | 16852 |
| 7 | 158778 |
| 8 | 1644732 |
| 9 | 18532810 |
| 10 | 225256740 |
| 11 | 2933174842 |
| 12 | 40687193548 |
| 13 | 598352302474 |
| 14 | 9290859275060 |
| 15 | 151779798262202 |
| 16 | 2600663778494172 |
| 17 | 46609915810749130 |
| 18 | 871645673599372868 |
| 19 | 16971639450858467002 |
| 20 | 343382806080459389676 |
[1,2,8,42,268,1994,16852,158778,1644732,18532810, 225256740,2933174842,40687193548,598352302474, 9290859275060,151779798262202,2600663778494172, 46609915810749130,871645673599372868, 16971639450858467002,343382806080459389676] |