The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 3 |
| 4 | 10 |
| 5 | 35 |
| 6 | 139 |
| 7 | 611 |
| 8 | 2925 |
| 9 | 15128 |
| 10 | 83903 |
| 11 | 495929 |
| 12 | 3108129 |
| 13 | 20565721 |
| 14 | 143134606 |
| 15 | 1044489265 |
| 16 | 7968879387 |
| 17 | 63407648443 |
| 18 | 525016067171 |
| 19 | 4514661402304 |
| 20 | 40245681692885 |
| 21 | 371319303282381 |
| 22 | 3540506731807277 |
| 23 | 34840411462506887 |
| 24 | 353394158240095874 |
| 25 | 3690577066014598575 |
[1,1,1,3,10,35,139,611,2925,15128,83903,495929, 3108129,20565721,143134606,1044489265,7968879387, 63407648443,525016067171,4514661402304, 40245681692885,371319303282381,3540506731807277, 34840411462506887,353394158240095874, 3690577066014598575] |