The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 104 |
| 6 | 572 |
| 7 | 3188 |
| 8 | 20956 |
| 9 | 161600 |
| 10 | 1295136 |
| 11 | 11618224 |
| 12 | 116270992 |
| 13 | 1227612062 |
| 14 | 13832165114 |
| 15 | 168852764168 |
| 16 | 2197057423482 |
[1,2,6,24,104,572,3188,20956,161600,1295136, 11618224,116270992,1227612062,13832165114, 168852764168,2197057423482] |