The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 1 |
| 5 | 1 |
| 6 | 1 |
| 7 | 1 |
| 8 | 1 |
| 9 | 3 |
| 10 | 7 |
| 11 | 13 |
| 12 | 23 |
| 13 | 55 |
| 14 | 135 |
| 15 | 381 |
| 16 | 1155 |
| 17 | 4259 |
| 18 | 15095 |
| 19 | 63361 |
| 20 | 271287 |
| 21 | 1364019 |
| 22 | 7046127 |
| 23 | 42849769 |
| 24 | 267209541 |
| 25 | 1961120087 |
| 26 | 14636956303 |
| 27 | 129172123843 |
| 28 | 1159685046407 |
| 29 | 12305875469689 |
[1,1,1,1,1,1,1,1,3,7,13,23,55,135,381,1155,4259, 15095,63361,271287,1364019,7046127,42849769, 267209541,1961120087,14636956303,129172123843, 1159685046407,12305875469689] |