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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 4 |
| 3 | 24 |
| 4 | 160 |
| 5 | 1440 |
| 6 | 18304 |
| 7 | 330624 |
| 8 | 8488960 |
| 9 | 309465600 |
| 10 | 16011372544 |
| 11 | 1174870185984 |
| 12 | 122233833963520 |
| 13 | 18023122242478080 |
| 14 | 3765668654914699264 |
| 15 | 1114515608405262434304 |
| 16 | 467221312005126294077440 |
| 17 | 277362415313453291571118080 |
| 18 | 233150477220213193598856331264 |
| 19 | 277465561009648882424932436803584 |
| 20 | 467466753447825987214906927108587520 |
[0,4,24,160,1440,18304,330624,8488960,309465600, 16011372544,1174870185984,122233833963520, 18023122242478080,3765668654914699264, 1114515608405262434304,467221312005126294077440, 277362415313453291571118080, 233150477220213193598856331264, 277465561009648882424932436803584, 467466753447825987214906927108587520] |