| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 1 |
| 5 | 2 |
| 6 | 12 |
| 7 | 24 |
| 8 | 113 |
| 9 | 232 |
| 10 | 1008 |
| 11 | 2122 |
| 12 | 8891 |
| 13 | 19110 |
| 14 | 78540 |
| 15 | 171694 |
| 16 | 697700 |
| 17 | 1546552 |
| 18 | 6240064 |
| 19 | 13992408 |
| 20 | 56192581 |
| 21 | 127231246 |
| 22 | 509314256 |
| 23 | 1162747842 |
| 24 | 4644046225 |
| 25 | 10677793584 |
[0,0,0,1,2,12,24,113,232,1008,2122,8891,19110, 78540,171694,697700,1546552,6240064,13992408, 56192581,127231246,509314256,1162747842, 4644046225,10677793584] |