The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 16 |
| 4 | 72 |
| 5 | 271 |
| 6 | 1024 |
| 7 | 3809 |
| 8 | 13968 |
| 9 | 50992 |
| 10 | 185364 |
| 11 | 672079 |
| 12 | 2433024 |
| 13 | 8798609 |
| 14 | 31797532 |
| 15 | 114864976 |
| 16 | 414821664 |
| 17 | 1497814207 |
| 18 | 5407599616 |
| 19 | 19521754897 |
| 20 | 70471314792 |
| 21 | 254385558128 |
| 22 | 918256161068 |
| 23 | 3314588702303 |
| 24 | 11964424716288 |
| 25 | 43186863073121 |
[1,4,16,72,271,1024,3809,13968,50992,185364, 672079,2433024,8798609,31797532,114864976, 414821664,1497814207,5407599616,19521754897, 70471314792,254385558128,918256161068, 3314588702303,11964424716288,43186863073121] |