The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 4 |
| 4 | 17 |
| 5 | 61 |
| 6 | 214 |
| 7 | 758 |
| 8 | 2723 |
| 9 | 9908 |
| 10 | 36444 |
| 11 | 135266 |
| 12 | 505859 |
| 13 | 1903888 |
| 14 | 7204872 |
| 15 | 27394664 |
| 16 | 104592935 |
| 17 | 400795842 |
| 18 | 1540820540 |
| 19 | 5940738674 |
| 20 | 22964779658 |
| 21 | 88983512781 |
| 22 | 345532572676 |
| 23 | 1344372335522 |
| 24 | 5239988770266 |
| 25 | 20457802016009 |
| 26 | 79992676367106 |
| 27 | 313224032098242 |
| 28 | 1228088671826971 |
[0,0,4,17,61,214,758,2723,9908,36444,135266, 505859,1903888,7204872,27394664,104592935, 400795842,1540820540,5940738674,22964779658, 88983512781,345532572676,1344372335522, 5239988770266,20457802016009,79992676367106, 313224032098242,1228088671826971] |