The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 9 |
| 3 | 71 |
| 4 | 549 |
| 5 | 4231 |
| 6 | 32589 |
| 7 | 250991 |
| 8 | 1933029 |
| 9 | 14887351 |
| 10 | 114655869 |
| 11 | 883029311 |
| 12 | 6800705109 |
| 13 | 52376052871 |
| 14 | 403377424749 |
| 15 | 3106636294031 |
| 16 | 23925952398789 |
| 17 | 184267208648791 |
| 18 | 1419145353851229 |
| 19 | 10929636098173151 |
| 20 | 84175271345046069 |
[0,1,9,71,549,4231,32589,250991,1933029,14887351, 114655869,883029311,6800705109,52376052871, 403377424749,3106636294031,23925952398789, 184267208648791,1419145353851229, 10929636098173151,84175271345046069] |