The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 4 |
| 3 | 16 |
| 4 | 56 |
| 5 | 256 |
| 6 | 1518 |
| 7 | 15896 |
| 8 | 171565 |
| 9 | 3217779 |
| 10 | 58858443 |
| 11 | 1927799742 |
| 12 | 63170771231 |
| 13 | 3671078892600 |
| 14 | 213376157401433 |
| 15 | 21677971544137049 |
[1,2,4,16,56,256,1518,15896,171565,3217779, 58858443,1927799742,63170771231,3671078892600, 213376157401433,21677971544137049] |