The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 9 |
| 3 | 48 |
| 4 | 278 |
| 5 | 1696 |
| 6 | 10736 |
| 7 | 69886 |
| 8 | 465019 |
| 9 | 3149476 |
| 10 | 21643433 |
| 11 | 150554144 |
| 12 | 1058101315 |
| 13 | 7502183626 |
| 14 | 53599160532 |
| 15 | 385494328218 |
| 16 | 2788827078507 |
| 17 | 20280590381098 |
| 18 | 148167425970522 |
| 19 | 1087007419753186 |
| 20 | 8004683588800899 |
[1,2,9,48,278,1696,10736,69886,465019,3149476, 21643433,150554144,1058101315,7502183626, 53599160532,385494328218,2788827078507, 20280590381098,148167425970522,1087007419753186, 8004683588800899] |