The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 6 |
| 3 | 54 |
| 4 | 540 |
| 5 | 5925 |
| 6 | 68753 |
| 7 | 830267 |
| 8 | 10324947 |
| 9 | 131329213 |
| 10 | 1700614790 |
| 11 | 22344117822 |
| 12 | 297132512955 |
| 13 | 3991542148276 |
| 14 | 54086668396101 |
| 15 | 738390401404546 |
| 16 | 10146440406910223 |
| 17 | 140227571720595241 |
| 18 | 1947883865390758591 |
| 19 | 27181029295364007844 |
| 20 | 380838895427784827916 |
[1,1,6,54,540,5925,68753,830267,10324947, 131329213,1700614790,22344117822,297132512955, 3991542148276,54086668396101,738390401404546, 10146440406910223,140227571720595241, 1947883865390758591,27181029295364007844, 380838895427784827916] |