The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 15 |
| 4 | 68 |
| 5 | 333 |
| 6 | 1727 |
| 7 | 9317 |
| 8 | 51758 |
| 9 | 294068 |
| 10 | 1700827 |
| 11 | 9980653 |
| 12 | 59274015 |
| 13 | 355592894 |
| 14 | 2151707068 |
| 15 | 13117292347 |
| 16 | 80486635016 |
| 17 | 496688096931 |
| 18 | 3080658090710 |
| 19 | 19194089036648 |
| 20 | 120075994871807 |
| 21 | 753943787632022 |
| 22 | 4749729156662452 |
| 23 | 30013614335452595 |
| 24 | 190184864457166325 |
| 25 | 1208214303761406925 |
[1,1,4,15,68,333,1727,9317,51758,294068,1700827, 9980653,59274015,355592894,2151707068,13117292347, 80486635016,496688096931,3080658090710, 19194089036648,120075994871807,753943787632022, 4749729156662452,30013614335452595, 190184864457166325,1208214303761406925] |