The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 13 |
| 4 | 55 |
| 5 | 231 |
| 6 | 987 |
| 7 | 4278 |
| 8 | 18711 |
| 9 | 82390 |
| 10 | 364793 |
| 11 | 1622556 |
| 12 | 7244419 |
| 13 | 32449158 |
| 14 | 145747290 |
| 15 | 656199048 |
| 16 | 2960596359 |
| 17 | 13382107227 |
| 18 | 60587421882 |
| 19 | 274712295550 |
| 20 | 1247233045905 |
| 21 | 5669390005950 |
| 22 | 25798654040580 |
| 23 | 117513750346200 |
| 24 | 535766200488675 |
| 25 | 2444698473079356 |
[1,1,3,13,55,231,987,4278,18711,82390,364793, 1622556,7244419,32449158,145747290,656199048, 2960596359,13382107227,60587421882,274712295550, 1247233045905,5669390005950,25798654040580, 117513750346200,535766200488675,2444698473079356] |