The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 12 |
| 4 | 54 |
| 5 | 203 |
| 6 | 913 |
| 7 | 3791 |
| 8 | 17421 |
| 9 | 76369 |
| 10 | 357010 |
| 11 | 1610906 |
| 12 | 7618852 |
| 13 | 35049764 |
| 14 | 167219609 |
| 15 | 780154851 |
| 16 | 3746904339 |
| 17 | 17660665005 |
| 18 | 85252847312 |
| 19 | 405012623438 |
| 20 | 1962958881010 |
| 21 | 9384294780340 |
| 22 | 45630045874621 |
| 23 | 219250204141161 |
| 24 | 1068911354389637 |
| 25 | 5157484620366595 |
| 26 | 25199960350383735 |
| 27 | 122013300433826613 |
[1,1,4,12,54,203,913,3791,17421,76369,357010, 1610906,7618852,35049764,167219609,780154851, 3746904339,17660665005,85252847312,405012623438, 1962958881010,9384294780340,45630045874621, 219250204141161,1068911354389637,5157484620366595, 25199960350383735,122013300433826613] |