The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 2 |
| 4 | 6 |
| 5 | 18 |
| 6 | 59 |
| 7 | 203 |
| 8 | 724 |
| 9 | 2643 |
| 10 | 9802 |
| 11 | 36755 |
| 12 | 138935 |
| 13 | 528406 |
| 14 | 2019419 |
| 15 | 7748125 |
| 16 | 29825844 |
| 17 | 115132729 |
| 18 | 445498768 |
| 19 | 1727434607 |
| 20 | 6710501025 |
| 21 | 26110567532 |
| 22 | 101744332967 |
| 23 | 396983837719 |
| 24 | 1550777652546 |
| 25 | 6064476854065 |
| 26 | 23739056348161 |
[0,0,1,2,6,18,59,203,724,2643,9802,36755,138935, 528406,2019419,7748125,29825844,115132729, 445498768,1727434607,6710501025,26110567532, 101744332967,396983837719,1550777652546, 6064476854065,23739056348161] |