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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 24 |
| 5 | 60 |
| 6 | 240 |
| 7 | 1260 |
| 8 | 108864 |
| 9 | 1149120 |
| 10 | 12160800 |
| 11 | 138045600 |
| 12 | 5605649280 |
| 13 | 122049607680 |
| 14 | 2378318604480 |
| 15 | 45712559692800 |
| 16 | 1529842399303680 |
| 17 | 47673689320857600 |
| 18 | 1382823169839820800 |
| 19 | 38831806109898547200 |
| 20 | 1378613101427645184000 |
[1,0,0,0,24,60,240,1260,108864,1149120,12160800, 138045600,5605649280,122049607680,2378318604480, 45712559692800,1529842399303680,47673689320857600, 1382823169839820800,38831806109898547200, 1378613101427645184000] |