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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 20 |
| 3 | 784 |
| 4 | 52480 |
| 5 | 5395456 |
| 6 | 791691264 |
| 7 | 157294854144 |
| 8 | 40683662475264 |
| 9 | 13288048674471936 |
| 10 | 5349739088314368000 |
| 11 | 2603081566154391552000 |
| 12 | 1506057980251484454912000 |
| 13 | 1021944601582419125993472000 |
[0,1,20,784,52480,5395456,791691264,157294854144, 40683662475264,13288048674471936, 5349739088314368000,2603081566154391552000, 1506057980251484454912000, 1021944601582419125993472000] |