The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 5 |
| 3 | 15 |
| 4 | 45 |
| 5 | 140 |
| 6 | 431 |
| 7 | 1326 |
| 8 | 4085 |
| 9 | 12580 |
| 10 | 38740 |
| 11 | 119305 |
| 12 | 367411 |
| 13 | 1131476 |
| 14 | 3484490 |
| 15 | 10730820 |
| 16 | 33046585 |
| 17 | 101770120 |
| 18 | 313410816 |
| 19 | 965178576 |
| 20 | 2972359720 |
| 21 | 9153665985 |
| 22 | 28189589705 |
| 23 | 86812537085 |
| 24 | 267347509271 |
| 25 | 823322219501 |
[1,1,5,15,45,140,431,1326,4085,12580,38740,119305, 367411,1131476,3484490,10730820,33046585, 101770120,313410816,965178576,2972359720, 9153665985,28189589705,86812537085,267347509271, 823322219501] |