The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 6 |
| 3 | 16 |
| 4 | 103 |
| 5 | 497 |
| 6 | 3253 |
| 7 | 19735 |
| 8 | 120843 |
| 9 | 681474 |
| 10 | 3561696 |
| 11 | 16938566 |
| 12 | 73500514 |
| 13 | 290751447 |
| 14 | 1052201890 |
| 15 | 3492397119 |
| 16 | 10666911842 |
| 17 | 30064448972 |
| 18 | 78409442414 |
| 19 | 189678764492 |
| 20 | 426539774378 |
| 21 | 893346071377 |
| 22 | 1745593733454 |
[1,1,6,16,103,497,3253,19735,120843,681474, 3561696,16938566,73500514,290751447,1052201890, 3492397119,10666911842,30064448972,78409442414, 189678764492,426539774378,893346071377, 1745593733454] |