The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 6 |
| 4 | 15 |
| 5 | 40 |
| 6 | 113 |
| 7 | 348 |
| 8 | 1148 |
| 9 | 4045 |
| 10 | 15203 |
| 11 | 60710 |
| 12 | 256688 |
| 13 | 1145887 |
| 14 | 5386283 |
| 15 | 26590338 |
| 16 | 137537012 |
| 17 | 743766652 |
| 18 | 4196681423 |
| 19 | 24661702224 |
| 20 | 150676068558 |
| 21 | 955611495432 |
| 22 | 6281965526173 |
| 23 | 42745748797360 |
| 24 | 300690981532778 |
[1,1,3,6,15,40,113,348,1148,4045,15203,60710, 256688,1145887,5386283,26590338,137537012, 743766652,4196681423,24661702224,150676068558, 955611495432,6281965526173,42745748797360, 300690981532778] |