The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 22 |
| 4 | 154 |
| 5 | 1306 |
| 6 | 12976 |
| 7 | 147484 |
| 8 | 1883932 |
| 9 | 26680924 |
| 10 | 414468496 |
| 11 | 7001104936 |
| 12 | 127677078904 |
| 13 | 2498712779512 |
| 14 | 52209534323584 |
| 15 | 1159559538626896 |
| 16 | 27269218041047056 |
| 17 | 676732851527182864 |
| 18 | 17669429275516846912 |
| 19 | 484087943980439097184 |
| 20 | 13882791112964223876256 |
[1,1,4,22,154,1306,12976,147484,1883932,26680924, 414468496,7001104936,127677078904,2498712779512, 52209534323584,1159559538626896,27269218041047056, 676732851527182864,17669429275516846912, 484087943980439097184,13882791112964223876256] |