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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 12 |
| 4 | 200 |
| 5 | 2280 |
| 6 | 22420 |
| 7 | 205212 |
| 8 | 1806000 |
| 9 | 15522960 |
| 10 | 131383340 |
| 11 | 1100093412 |
| 12 | 9138243400 |
| 13 | 75445046040 |
| 14 | 619838752260 |
| 15 | 5072272077612 |
| 16 | 41371548418400 |
| 17 | 336519691295520 |
| 18 | 2730963319321180 |
| 19 | 22119245290765812 |
| 20 | 178854325039467000 |
| 21 | 1444135501669535400 |
[0,0,12,200,2280,22420,205212,1806000,15522960, 131383340,1100093412,9138243400,75445046040, 619838752260,5072272077612,41371548418400, 336519691295520,2730963319321180, 22119245290765812,178854325039467000, 1444135501669535400] |