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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 4 |
| 2 | 8 |
| 3 | 24 |
| 4 | 96 |
| 5 | 480 |
| 6 | 2880 |
| 7 | 20160 |
| 8 | 161280 |
| 9 | 1451520 |
| 10 | 14515200 |
| 11 | 159667200 |
| 12 | 1916006400 |
| 13 | 24908083200 |
| 14 | 348713164800 |
| 15 | 5230697472000 |
| 16 | 83691159552000 |
| 17 | 1422749712384000 |
| 18 | 25609494822912000 |
| 19 | 486580401635328000 |
| 20 | 9731608032706560000 |
| 21 | 204363768686837760000 |
[0,4,8,24,96,480,2880,20160,161280,1451520, 14515200,159667200,1916006400,24908083200, 348713164800,5230697472000,83691159552000, 1422749712384000,25609494822912000, 486580401635328000,9731608032706560000, 204363768686837760000] |