The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 18 |
| 5 | 61 |
| 6 | 218 |
| 7 | 804 |
| 8 | 3052 |
| 9 | 11831 |
| 10 | 46646 |
| 11 | 186487 |
| 12 | 754177 |
| 13 | 3079767 |
| 14 | 12681568 |
| 15 | 52595999 |
| 16 | 219515014 |
| 17 | 921264092 |
| 18 | 3885468897 |
| 19 | 16459470468 |
| 20 | 70001813240 |
| 21 | 298785285316 |
| 22 | 1279450906737 |
| 23 | 5495145204550 |
| 24 | 23665623371950 |
| 25 | 102175095587827 |
[1,1,2,6,18,61,218,804,3052,11831,46646,186487, 754177,3079767,12681568,52595999,219515014, 921264092,3885468897,16459470468,70001813240, 298785285316,1279450906737,5495145204550, 23665623371950,102175095587827] |