The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 18 |
| 4 | 527 |
| 5 | 3218 |
| 6 | 138634 |
| 7 | 957857 |
| 8 | 49120018 |
| 9 | 20473889132 |
| 10 | 156766505690 |
| 11 | 74324776 |
| 12 | 203270 |
| 13 | 4686290685410776 |
| 14 | 37541445026997947 |
| 15 | 2445882966702428971 |
| 16 | 13279375056930183 |
| 17 | 42712 |
| 18 | 743757817682170309535791 |
[1,4,18,527,3218,138634,957857,49120018, 20473889132,156766505690,74324776,203270, 4686290685410776,37541445026997947, 2445882966702428971,13279375056930183,42712, 743757817682170309535791] |