The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 7 |
| 4 | 19 |
| 5 | 66 |
| 6 | 212 |
| 7 | 743 |
| 8 | 2487 |
| 9 | 9012 |
| 10 | 31177 |
| 11 | 113775 |
| 12 | 404584 |
| 13 | 1490726 |
| 14 | 5376676 |
| 15 | 20028981 |
| 16 | 73068861 |
| 17 | 273659672 |
| 18 | 1009921813 |
| 19 | 3801386137 |
| 20 | 14125670266 |
| 21 | 53477758556 |
| 22 | 199950414035 |
| 23 | 759566205693 |
| 24 | 2857261603610 |
| 25 | 10889590477287 |
| 26 | 41136917417501 |
| 27 | 157329747348492 |
[1,1,2,7,19,66,212,743,2487,9012,31177,113775, 404584,1490726,5376676,20028981,73068861, 273659672,1009921813,3801386137,14125670266, 53477758556,199950414035,759566205693, 2857261603610,10889590477287,41136917417501, 157329747348492] |