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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 20 |
| 3 | 1120 |
| 4 | 30800 |
| 5 | 1121120 |
| 6 | 152472320 |
| 7 | 8277068800 |
| 8 | 523524601600 |
| 9 | 340290991040000 |
| 10 | 27631628472448000 |
| 11 | 2491870494969856000 |
| 12 | 741331472253532160000 |
| 13 | 80177849999112785920000 |
| 14 | 9392262428467497779200000 |
| 15 | 3554032102932101159649280000 |
| 16 | 480238587908700169197608960000 |
[1,2,20,1120,30800,1121120,152472320,8277068800, 523524601600,340290991040000,27631628472448000, 2491870494969856000,741331472253532160000, 80177849999112785920000,9392262428467497779200000, 3554032102932101159649280000, 480238587908700169197608960000] |