The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 8 |
| 5 | 17 |
| 6 | 40 |
| 7 | 105 |
| 8 | 304 |
| 9 | 958 |
| 10 | 3255 |
| 11 | 11851 |
| 12 | 46096 |
| 13 | 191648 |
| 14 | 854551 |
| 15 | 4101826 |
| 16 | 21213282 |
| 17 | 117747119 |
| 18 | 695773801 |
| 19 | 4332490151 |
| 20 | 28149712546 |
| 21 | 189300600481 |
| 22 | 1309755334070 |
| 23 | 9286984108299 |
| 24 | 67327505784439 |
| 25 | 498502290046850 |
| 26 | 3769028024302567 |
| 27 | 29115361551715499 |
[1,1,2,4,8,17,40,105,304,958,3255,11851,46096, 191648,854551,4101826,21213282,117747119, 695773801,4332490151,28149712546,189300600481, 1309755334070,9286984108299,67327505784439, 498502290046850,3769028024302567, 29115361551715499] |