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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 12 |
| 4 | 24 |
| 5 | 80 |
| 6 | 2520 |
| 7 | 17136 |
| 8 | 124320 |
| 9 | 2462400 |
| 10 | 30965760 |
| 11 | 372113280 |
| 12 | 7014807360 |
| 13 | 122840789760 |
| 14 | 2078973921024 |
| 15 | 43236813312000 |
| 16 | 932206147891200 |
| 17 | 20090534745415680 |
| 18 | 480054835899371520 |
| 19 | 12126262777282805760 |
| 20 | 313198020852233932800 |
[1,0,0,12,24,80,2520,17136,124320,2462400, 30965760,372113280,7014807360,122840789760, 2078973921024,43236813312000,932206147891200, 20090534745415680,480054835899371520, 12126262777282805760,313198020852233932800] |