The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 40 |
| 3 | 176 |
| 4 | 828 |
| 5 | 3253 |
| 6 | 13396 |
| 7 | 53864 |
| 8 | 215761 |
| 9 | 868457 |
| 10 | 3463137 |
| 11 | 13843993 |
| 12 | 55410869 |
| 13 | 221698185 |
| 14 | 886916925 |
| 15 | 3547643840 |
[1,4,40,176,828,3253,13396,53864,215761,868457, 3463137,13843993,55410869,221698185,886916925, 3547643840] |