| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 15 |
| 4 | 111 |
| 5 | 3936 |
| 6 | 28320 |
| 7 | 999855 |
| 8 | 7193295 |
| 9 | 253959360 |
| 10 | 1827068736 |
| 11 | 64504677711 |
| 12 | 464068265775 |
| 13 | 16383934179360 |
| 14 | 117871512438240 |
| 15 | 4161454776879855 |
| 16 | 29938900091047311 |
| 17 | 1056993129393303936 |
| 18 | 7604362751613578880 |
[0,0,15,111,3936,28320,999855,7193295,253959360, 1827068736,64504677711,464068265775, 16383934179360,117871512438240,4161454776879855, 29938900091047311,1056993129393303936, 7604362751613578880] |