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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 24 |
| 5 | 60 |
| 6 | 240 |
| 7 | 1260 |
| 8 | 88704 |
| 9 | 786240 |
| 10 | 7171200 |
| 11 | 71517600 |
| 12 | 2937876480 |
| 13 | 51372921600 |
| 14 | 807474769920 |
| 15 | 12722062953600 |
| 16 | 430490106224640 |
| 17 | 11120066371814400 |
| 18 | 256635966514636800 |
| 19 | 5726578592094796800 |
| 20 | 191258904944891289600 |
| 21 | 6233110401650436864000 |
| 22 | 189751022005164912230400 |
[1,0,0,0,24,60,240,1260,88704,786240,7171200, 71517600,2937876480,51372921600,807474769920, 12722062953600,430490106224640,11120066371814400, 256635966514636800,5726578592094796800, 191258904944891289600,6233110401650436864000, 189751022005164912230400] |