The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 11 |
| 5 | 37 |
| 6 | 125 |
| 7 | 415 |
| 8 | 1371 |
| 9 | 4501 |
| 10 | 14725 |
| 11 | 48031 |
| 12 | 156355 |
| 13 | 508197 |
| 14 | 1649933 |
| 15 | 5352255 |
| 16 | 17351563 |
| 17 | 56226389 |
| 18 | 182134837 |
[0,1,3,11,37,125,415,1371,4501,14725,48031,156355, 508197,1649933,5352255,17351563,56226389, 182134837] |