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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 49920 |
| 5 | 18936480 |
| 6 | 1293857280 |
| 7 | 34839270480 |
| 8 | 518880929280 |
| 9 | 5122755187200 |
| 10 | 37376074229760 |
| 11 | 216261381584160 |
| 12 | 1041571537839360 |
| 13 | 4323020652281760 |
| 14 | 15864787390932480 |
| 15 | 52496402135289840 |
| 16 | 159036030441200640 |
| 17 | 446469968164496640 |
| 18 | 1172916400659517440 |
[0,0,0,0,49920,18936480,1293857280,34839270480, 518880929280,5122755187200,37376074229760, 216261381584160,1041571537839360,4323020652281760, 15864787390932480,52496402135289840, 159036030441200640,446469968164496640, 1172916400659517440] |