The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 9 |
| 5 | 41 |
| 6 | 133 |
| 7 | 673 |
| 8 | 2737 |
| 9 | 15130 |
| 10 | 72181 |
| 11 | 430739 |
| 12 | 2320825 |
| 13 | 14815529 |
| 14 | 88005541 |
| 15 | 596681296 |
| 16 | 3843559137 |
| 17 | 27515587661 |
| 18 | 189933449365 |
| 19 | 1428716457761 |
| 20 | 10474213334761 |
| 21 | 82448447397646 |
| 22 | 637534807917701 |
| 23 | 5233087759204967 |
| 24 | 42445677865505425 |
| 25 | 362213650380301201 |
[0,1,1,4,9,41,133,673,2737,15130,72181,430739, 2320825,14815529,88005541,596681296,3843559137, 27515587661,189933449365,1428716457761, 10474213334761,82448447397646,637534807917701, 5233087759204967,42445677865505425, 362213650380301201] |