The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 11 |
| 5 | 39 |
| 6 | 161 |
| 7 | 784 |
| 8 | 4368 |
| 9 | 27260 |
| 10 | 189540 |
| 11 | 1448860 |
| 12 | 12076408 |
| 13 | 109102564 |
| 14 | 1061259548 |
| 15 | 11060323280 |
| 16 | 122963473024 |
| 17 | 1452414435968 |
| 18 | 18164949751872 |
| 19 | 239807221886128 |
| 20 | 3332441297971360 |
| 21 | 48624372236312912 |
| 22 | 743273838888233264 |
| 23 | 11878134680411900928 |
[1,1,2,4,11,39,161,784,4368,27260,189540,1448860, 12076408,109102564,1061259548,11060323280, 122963473024,1452414435968,18164949751872, 239807221886128,3332441297971360, 48624372236312912,743273838888233264, 11878134680411900928] |