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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 2 |
| 3 | 6 |
| 4 | 70 |
| 5 | 700 |
| 6 | 10268 |
| 7 | 171108 |
| 8 | 3404280 |
| 9 | 77158800 |
| 10 | 1977004752 |
| 11 | 56398061280 |
| 12 | 1774104501024 |
| 13 | 61004101979808 |
| 14 | 2276675340590688 |
| 15 | 91652238159138720 |
| 16 | 3959064663300753408 |
| 17 | 182664424801700783616 |
| 18 | 8965482639644918631168 |
| 19 | 466444129035055869430272 |
[1,0,2,6,70,700,10268,171108,3404280,77158800, 1977004752,56398061280,1774104501024, 61004101979808,2276675340590688,91652238159138720, 3959064663300753408,182664424801700783616, 8965482639644918631168,466444129035055869430272] |