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 | 7 |
| 5 | 25 |
| 6 | 105 |
| 7 | 547 |
| 8 | 3367 |
| 9 | 24033 |
| 10 | 195169 |
| 11 | 1777651 |
| 12 | 17950551 |
| 13 | 199059673 |
| 14 | 2405063017 |
| 15 | 31448531955 |
| 16 | 442501797655 |
| 17 | 6666753146497 |
| 18 | 107081325959937 |
| 19 | 1826636018849443 |
| 20 | 32980276187719399 |
| 21 | 628351055737088601 |
[1,1,1,3,7,25,105,547,3367,24033,195169,1777651, 17950551,199059673,2405063017,31448531955, 442501797655,6666753146497,107081325959937, 1826636018849443,32980276187719399, 628351055737088601] |