The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 4 |
| 5 | 10 |
| 6 | 27 |
| 7 | 83 |
| 8 | 281 |
| 9 | 1035 |
| 10 | 4127 |
| 11 | 17656 |
| 12 | 80598 |
| 13 | 390649 |
| 14 | 2001779 |
| 15 | 10804600 |
| 16 | 61230207 |
| 17 | 363291235 |
| 18 | 2251035412 |
| 19 | 14533496547 |
| 20 | 97575061512 |
| 21 | 679975389773 |
| 22 | 4910327064257 |
| 23 | 36688562599092 |
| 24 | 283236504667511 |
| 25 | 2256366104654141 |
| 26 | 18526697776919183 |
| 27 | 156616975726597637 |
[1,1,1,2,4,10,27,83,281,1035,4127,17656,80598, 390649,2001779,10804600,61230207,363291235, 2251035412,14533496547,97575061512,679975389773, 4910327064257,36688562599092,283236504667511, 2256366104654141,18526697776919183, 156616975726597637] |