The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 5 |
| 4 | 16 |
| 5 | 52 |
| 6 | 170 |
| 7 | 581 |
| 8 | 2082 |
| 9 | 7647 |
| 10 | 28508 |
| 11 | 107906 |
| 12 | 414484 |
| 13 | 1611854 |
| 14 | 6332018 |
| 15 | 25103351 |
| 16 | 100354887 |
| 17 | 404032355 |
| 18 | 1636789195 |
| 19 | 6669626502 |
| 20 | 27324758600 |
| 21 | 112493883858 |
| 22 | 465159225696 |
| 23 | 1931115979433 |
| 24 | 8047040424824 |
| 25 | 33649572444003 |
| 26 | 141165249544075 |
| 27 | 593988710389378 |
| 28 | 2506331355166934 |
[1,1,2,5,16,52,170,581,2082,7647,28508,107906, 414484,1611854,6332018,25103351,100354887, 404032355,1636789195,6669626502,27324758600, 112493883858,465159225696,1931115979433, 8047040424824,33649572444003,141165249544075, 593988710389378,2506331355166934] |