The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 1 |
| 5 | 1 |
| 6 | 5 |
| 7 | 21 |
| 8 | 61 |
| 9 | 266 |
| 10 | 891 |
| 11 | 3074 |
| 12 | 18035 |
| 13 | 122510 |
| 14 | 915879 |
| 15 | 8736750 |
| 16 | 97430523 |
| 17 | 1219777035 |
| 18 | 17287269221 |
[1,1,1,1,1,5,21,61,266,891,3074,18035,122510, 915879,8736750,97430523,1219777035,17287269221] |