The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 1 |
| 4 | 2 |
| 5 | 5 |
| 6 | 15 |
| 7 | 50 |
| 8 | 181 |
| 9 | 697 |
| 10 | 2821 |
| 11 | 11892 |
| 12 | 51874 |
| 13 | 232974 |
| 14 | 1073070 |
| 15 | 5053029 |
| 16 | 24264565 |
| 17 | 118570292 |
| 18 | 588567257 |
| 19 | 2963358162 |
| 20 | 15114174106 |
| 21 | 78004013763 |
| 22 | 406971280545 |
| 23 | 2144659072330 |
| 24 | 11407141925639 |
| 25 | 61197287846831 |
[1,0,1,1,2,5,15,50,181,697,2821,11892,51874, 232974,1073070,5053029,24264565,118570292, 588567257,2963358162,15114174106,78004013763, 406971280545,2144659072330,11407141925639, 61197287846831] |