The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 10 |
| 5 | 28 |
| 6 | 116 |
| 7 | 576 |
| 8 | 3634 |
| 9 | 26620 |
| 10 | 223440 |
| 11 | 2100964 |
| 12 | 21888712 |
| 13 | 250062982 |
| 14 | 3108430640 |
[1,2,4,10,28,116,576,3634,26620,223440,2100964, 21888712,250062982,3108430640] |