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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 2 |
| 3 | 3 |
| 4 | 80 |
| 5 | 570 |
| 6 | 12744 |
| 7 | 198660 |
| 8 | 4969152 |
| 9 | 119968128 |
| 10 | 3607836480 |
| 11 | 115031711520 |
| 12 | 4163170478400 |
| 13 | 162622297300320 |
| 14 | 6952158785424384 |
| 15 | 319741032356928000 |
| 16 | 15818989359665802240 |
| 17 | 835755271882288128000 |
| 18 | 47015148988105365288960 |
| 19 | 2804276310235518168161280 |
[1,0,2,3,80,570,12744,198660,4969152,119968128, 3607836480,115031711520,4163170478400, 162622297300320,6952158785424384, 319741032356928000,15818989359665802240, 835755271882288128000,47015148988105365288960, 2804276310235518168161280] |