The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 5 |
| 3 | 37 |
| 4 | 245 |
| 5 | 1669 |
| 6 | 11285 |
| 7 | 76453 |
| 8 | 517685 |
| 9 | 3505861 |
| 10 | 23741525 |
| 11 | 160777957 |
| 12 | 1088788085 |
| 13 | 7373275909 |
| 14 | 49931836565 |
| 15 | 338138493733 |
| 16 | 2289874507445 |
| 17 | 15507034462021 |
| 18 | 105013666399445 |
| 19 | 711152745541477 |
| 20 | 4815927724500725 |
| 21 | 32613471569001349 |
[0,1,5,37,245,1669,11285,76453,517685,3505861, 23741525,160777957,1088788085,7373275909, 49931836565,338138493733,2289874507445, 15507034462021,105013666399445,711152745541477, 4815927724500725,32613471569001349] |