The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 18 |
| 4 | 172 |
| 5 | 2343 |
| 6 | 42439 |
| 7 | 976050 |
| 8 | 27583338 |
| 9 | 934173632 |
| 10 | 37180409223 |
| 11 | 1711870023666 |
| 12 | 90007747560742 |
| 13 | 5346164992890599 |
| 14 | 355442084718552178 |
| 15 | 26244000000000000000 |
| 16 | 2137205155719002036203 |
| 17 | 190811368062993357765186 |
| 18 | 18577775646585813239195436 |
| 19 | 1963166636163973976912956096 |
[1,1,3,18,172,2343,42439,976050,27583338, 934173632,37180409223,1711870023666, 90007747560742,5346164992890599, 355442084718552178,26244000000000000000, 2137205155719002036203,190811368062993357765186, 18577775646585813239195436, 1963166636163973976912956096] |