| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 0 |
| 6 | 60 |
| 7 | 1080 |
| 8 | 11970 |
| 9 | 105840 |
| 10 | 821952 |
| 11 | 5874480 |
| 12 | 39713490 |
| 13 | 258136200 |
| 14 | 1631272140 |
| 15 | 10096734312 |
| 16 | 61536365730 |
| 17 | 370710950400 |
| 18 | 2213749552980 |
| 19 | 13132080672480 |
| 20 | 77509456122366 |
| 21 | 455754569691600 |
[0,0,0,0,0,60,1080,11970,105840,821952,5874480, 39713490,258136200,1631272140,10096734312, 61536365730,370710950400,2213749552980, 13132080672480,77509456122366,455754569691600] |