The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 3 |
| 3 | 7 |
| 4 | 33 |
| 5 | 285 |
| 6 | 3648 |
| 7 | 61306 |
| 8 | 1270440 |
| 9 | 31244205 |
| 10 | 888288960 |
| 11 | 28640745684 |
| 12 | 1032065614715 |
| 13 | 41087944243649 |
| 14 | 1790413981105727 |
| 15 | 84737880414848784 |
| 16 | 4327877295100145382 |
| 17 | 237218770042549151701 |
| 18 | 13887772416031152573506 |
[1,2,3,7,33,285,3648,61306,1270440,31244205, 888288960,28640745684,1032065614715, 41087944243649,1790413981105727,84737880414848784, 4327877295100145382,237218770042549151701, 13887772416031152573506] |