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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 8 |
| 5 | 20 |
| 6 | 10 |
| 7 | 280 |
| 8 | 3360 |
| 9 | 20440 |
| 10 | 67200 |
| 11 | 462000 |
| 12 | 7407400 |
| 13 | 73673600 |
| 14 | 482081600 |
| 15 | 3364761400 |
| 16 | 47311264000 |
| 17 | 657536880000 |
| 18 | 6586994814400 |
| 19 | 58707179731200 |
| 20 | 740032028736000 |
| 21 | 11832726841936000 |
| 22 | 161121297104768000 |
| 23 | 1857897194273120000 |
| 24 | 23875495204536976000 |
[1,0,0,1,8,20,10,280,3360,20440,67200,462000, 7407400,73673600,482081600,3364761400,47311264000, 657536880000,6586994814400,58707179731200, 740032028736000,11832726841936000, 161121297104768000,1857897194273120000, 23875495204536976000] |