The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | -1 |
| 1 | 0 |
| 2 | 2 |
| 3 | 10 |
| 4 | 42 |
| 5 | 168 |
| 6 | 660 |
| 7 | 2574 |
| 8 | 10010 |
| 9 | 38896 |
| 10 | 151164 |
| 11 | 587860 |
| 12 | 2288132 |
| 13 | 8914800 |
| 14 | 34767720 |
| 15 | 135727830 |
| 16 | 530365050 |
| 17 | 2074316640 |
| 18 | 8119857900 |
| 19 | 31810737420 |
| 20 | 124718287980 |
| 21 | 489325340400 |
| 22 | 1921133836440 |
| 23 | 7547311500300 |
| 24 | 29667795388452 |
| 25 | 116686713634848 |
| 26 | 459183826803800 |
[-1,0,2,10,42,168,660,2574,10010,38896,151164, 587860,2288132,8914800,34767720,135727830, 530365050,2074316640,8119857900,31810737420, 124718287980,489325340400,1921133836440, 7547311500300,29667795388452,116686713634848, 459183826803800] |