The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 4 |
| 3 | 8 |
| 4 | 18 |
| 5 | 44 |
| 6 | 122 |
| 7 | 362 |
| 8 | 1162 |
| 9 | 3914 |
| 10 | 13648 |
| 11 | 48734 |
| 12 | 176906 |
| 13 | 649532 |
| 14 | 2405236 |
| 15 | 8964800 |
| 16 | 33588234 |
| 17 | 126390032 |
| 18 | 477353376 |
| 19 | 1808676326 |
| 20 | 6872485104 |
| 21 | 26179922024 |
| 22 | 99957747388 |
| 23 | 382443112538 |
| 24 | 1466024067850 |
| 25 | 5629516646996 |
| 26 | 21651955485304 |
| 27 | 83400061453514 |
[1,2,4,8,18,44,122,362,1162,3914,13648,48734, 176906,649532,2405236,8964800,33588234,126390032, 477353376,1808676326,6872485104,26179922024, 99957747388,382443112538,1466024067850, 5629516646996,21651955485304,83400061453514] |