The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 22 |
| 4 | 112 |
| 5 | 589 |
| 6 | 3100 |
| 7 | 16393 |
| 8 | 86800 |
| 9 | 459994 |
| 10 | 2438536 |
| 11 | 12929377 |
| 12 | 68557720 |
| 13 | 363537265 |
| 14 | 1927735708 |
| 15 | 10222301758 |
| 16 | 54206461120 |
| 17 | 287444443765 |
| 18 | 1524252798580 |
| 19 | 8082769233721 |
| 20 | 42861108613288 |
| 21 | 227282835266626 |
| 22 | 1205229864917272 |
[1,4,22,112,589,3100,16393,86800,459994,2438536, 12929377,68557720,363537265,1927735708, 10222301758,54206461120,287444443765, 1524252798580,8082769233721,42861108613288, 227282835266626,1205229864917272] |