| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 6 |
| 3 | 150 |
| 4 | 8400 |
| 5 | 834120 |
| 6 | 129230640 |
| 7 | 28805736960 |
| 8 | 8734434508800 |
| 9 | 3457819037312640 |
| 10 | 1732015476199008000 |
| 11 | 1070842073499515116800 |
| 12 | 800968643959240044288000 |
| 13 | 712900933001021056900608000 |
| 14 | 744602794912654938776355840000 |
| 15 | 901893717412811100821094451200000 |
[1,6,150,8400,834120,129230640,28805736960, 8734434508800,3457819037312640, 1732015476199008000,1070842073499515116800, 800968643959240044288000, 712900933001021056900608000, 744602794912654938776355840000, 901893717412811100821094451200000] |