The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 2 |
| 3 | 4 |
| 4 | 11 |
| 5 | 31 |
| 6 | 94 |
| 7 | 298 |
| 8 | 977 |
| 9 | 3283 |
| 10 | 11243 |
| 11 | 39087 |
| 12 | 137569 |
| 13 | 489171 |
| 14 | 1754596 |
| 15 | 6340756 |
| 16 | 23063731 |
| 17 | 84372061 |
| 18 | 310216081 |
| 19 | 1145748061 |
| 20 | 4248861631 |
| 21 | 15814069951 |
| 22 | 59054807821 |
| 23 | 221197379221 |
| 24 | 830819449003 |
| 25 | 3128511421663 |
| 26 | 11808294045071 |
[0,0,2,4,11,31,94,298,977,3283,11243,39087,137569, 489171,1754596,6340756,23063731,84372061, 310216081,1145748061,4248861631,15814069951, 59054807821,221197379221,830819449003, 3128511421663,11808294045071] |