The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 17 |
| 3 | 80 |
| 4 | 369 |
| 5 | 1700 |
| 6 | 7841 |
| 7 | 36160 |
| 8 | 166753 |
| 9 | 768996 |
| 10 | 3546289 |
| 11 | 16354000 |
| 12 | 75417809 |
| 13 | 347795396 |
| 14 | 1603886913 |
| 15 | 7396455680 |
| 16 | 34109360321 |
| 17 | 157298104900 |
| 18 | 725393076049 |
| 19 | 3345209499600 |
| 20 | 15426707209777 |
| 21 | 71141522037604 |
| 22 | 328074947492321 |
| 23 | 1512944453384000 |
| 24 | 6977067089461281 |
[1,4,17,80,369,1700,7841,36160,166753,768996, 3546289,16354000,75417809,347795396,1603886913, 7396455680,34109360321,157298104900,725393076049, 3345209499600,15426707209777,71141522037604, 328074947492321,1512944453384000,6977067089461281] |