The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 8 |
| 4 | 23 |
| 5 | 70 |
| 6 | 222 |
| 7 | 726 |
| 8 | 2431 |
| 9 | 8294 |
| 10 | 28730 |
| 11 | 100776 |
| 12 | 357238 |
| 13 | 1277788 |
| 14 | 4605980 |
| 15 | 16715250 |
| 16 | 61020495 |
| 17 | 223931910 |
| 18 | 825632610 |
| 19 | 3056887680 |
| 20 | 11360977650 |
| 21 | 42368413620 |
| 22 | 158498860260 |
| 23 | 594636663660 |
| 24 | 2236748680998 |
| 25 | 8433988655580 |
| 26 | 31872759742852 |
| 27 | 120699748759856 |
[1,3,8,23,70,222,726,2431,8294,28730,100776, 357238,1277788,4605980,16715250,61020495, 223931910,825632610,3056887680,11360977650, 42368413620,158498860260,594636663660, 2236748680998,8433988655580,31872759742852, 120699748759856] |