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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 2 |
| 3 | 6 |
| 4 | 216 |
| 5 | 2040 |
| 6 | 111240 |
| 7 | 2164680 |
| 8 | 159391680 |
| 9 | 5247305280 |
| 10 | 491431600800 |
| 11 | 24437592194400 |
| 12 | 2800955712804480 |
| 13 | 195393943295591040 |
| 14 | 26699221909806526080 |
| 15 | 2479967110139382864000 |
| 16 | 396503602252401676032000 |
| 17 | 47167550656581451928832000 |
[1,0,2,6,216,2040,111240,2164680,159391680, 5247305280,491431600800,24437592194400, 2800955712804480,195393943295591040, 26699221909806526080,2479967110139382864000, 396503602252401676032000, 47167550656581451928832000] |