The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 8 |
| 3 | 44 |
| 4 | 296 |
| 5 | 2312 |
| 6 | 20384 |
| 7 | 199376 |
| 8 | 2138336 |
| 9 | 24936416 |
| 10 | 314142848 |
| 11 | 4252773824 |
| 12 | 61594847360 |
| 13 | 950757812864 |
| 14 | 15586971531776 |
| 15 | 270569513970944 |
| 16 | 4959071121374720 |
| 17 | 95721139472072192 |
| 18 | 1941212789888952320 |
| 19 | 41271304403571227648 |
| 20 | 918030912312297752576 |
| 21 | 21325054720042613565440 |
[1,2,8,44,296,2312,20384,199376,2138336,24936416, 314142848,4252773824,61594847360,950757812864, 15586971531776,270569513970944,4959071121374720, 95721139472072192,1941212789888952320, 41271304403571227648,918030912312297752576, 21325054720042613565440] |