The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 15 |
| 4 | 73 |
| 5 | 373 |
| 6 | 2036 |
| 7 | 11518 |
| 8 | 67108 |
| 9 | 399596 |
| 10 | 2421477 |
| 11 | 14883232 |
| 12 | 92561649 |
| 13 | 581401130 |
| 14 | 3683031612 |
| 15 | 23502839520 |
| 16 | 150944260610 |
| 17 | 974905750378 |
| 18 | 6328238976958 |
| 19 | 41261578774953 |
| 20 | 270119042203681 |
| 21 | 1774773646080126 |
| 22 | 11699419572947070 |
| 23 | 77355905980770122 |
| 24 | 512885661648043804 |
[1,1,4,15,73,373,2036,11518,67108,399596,2421477, 14883232,92561649,581401130,3683031612, 23502839520,150944260610,974905750378, 6328238976958,41261578774953,270119042203681, 1774773646080126,11699419572947070, 77355905980770122,512885661648043804] |