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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 6 |
| 4 | 24 |
| 5 | 120 |
| 6 | 23760 |
| 7 | 327600 |
| 8 | 5201280 |
| 9 | 1283688000 |
| 10 | 37574409600 |
| 11 | 1219438281600 |
| 12 | 378254710310400 |
| 13 | 19092171351052800 |
| 14 | 1045282110435763200 |
| 15 | 394211859168070944000 |
| 16 | 30499777423295212032000 |
| 17 | 2523689643597315088896000 |
| 18 | 1125362204955051396299366400 |
[1,0,0,6,24,120,23760,327600,5201280,1283688000, 37574409600,1219438281600,378254710310400, 19092171351052800,1045282110435763200, 394211859168070944000,30499777423295212032000, 2523689643597315088896000, 1125362204955051396299366400] |