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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 30 |
| 4 | 600 |
| 5 | 17980 |
| 6 | 701280 |
| 7 | 33904822 |
| 8 | 1956209024 |
| 9 | 131229583596 |
| 10 | 10037690006400 |
| 11 | 862338700678884 |
| 12 | 82216457762199552 |
| 13 | 8614684257283258102 |
| 14 | 984021646462806049280 |
| 15 | 121700458370370286320750 |
| 16 | 16202120194768984283381760 |
| 17 | 2310243113824870018738497732 |
| 18 | 351271199659878407029587277824 |
| 19 | 56734597035765569017356665543968 |
| 20 | 9700307843128908988513920450560000 |
[1,2,30,600,17980,701280,33904822,1956209024, 131229583596,10037690006400,862338700678884, 82216457762199552,8614684257283258102, 984021646462806049280,121700458370370286320750, 16202120194768984283381760, 2310243113824870018738497732, 351271199659878407029587277824, 56734597035765569017356665543968, 9700307843128908988513920450560000] |