The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 23 |
| 4 | 102 |
| 5 | 496 |
| 6 | 2570 |
| 7 | 13959 |
| 8 | 78682 |
| 9 | 457243 |
| 10 | 2727360 |
| 11 | 16647048 |
| 12 | 103759186 |
| 13 | 659500772 |
| 14 | 4271197824 |
| 15 | 28175622291 |
| 16 | 189321228022 |
| 17 | 1296246842443 |
| 18 | 9049626101836 |
| 19 | 64481397834665 |
| 20 | 469461395956168 |
| 21 | 3497006117588399 |
| 22 | 26688813841105524 |
| 23 | 208977790442594368 |
| 24 | 1680981707733908594 |
[1,2,6,23,102,496,2570,13959,78682,457243,2727360, 16647048,103759186,659500772,4271197824, 28175622291,189321228022,1296246842443, 9049626101836,64481397834665,469461395956168, 3497006117588399,26688813841105524, 208977790442594368,1680981707733908594] |