The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 1 |
| 5 | 1 |
| 6 | 5 |
| 7 | 15 |
| 8 | 35 |
| 9 | 70 |
| 10 | 574 |
| 11 | 2674 |
| 12 | 9274 |
| 13 | 26599 |
| 14 | 305747 |
| 15 | 1944033 |
| 16 | 8995805 |
| 17 | 33757360 |
| 18 | 498851248 |
| 19 | 4017418768 |
| 20 | 23236611280 |
| 21 | 107709888805 |
| 22 | 1945409895065 |
| 23 | 18965460022971 |
| 24 | 131635127294783 |
| 25 | 726401013530416 |
| 26 | 15505381392117616 |
| 27 | 177447751441161616 |
[1,1,1,1,1,1,5,15,35,70,574,2674,9274,26599, 305747,1944033,8995805,33757360,498851248, 4017418768,23236611280,107709888805,1945409895065, 18965460022971,131635127294783,726401013530416, 15505381392117616,177447751441161616] |