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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 2 |
| 2 | 24 |
| 3 | 720 |
| 4 | 10080 |
| 5 | 157500 |
| 6 | 2128896 |
| 7 | 28420392 |
| 8 | 363242880 |
| 9 | 4552582320 |
| 10 | 55888690000 |
| 11 | 676114951512 |
| 12 | 8074566549504 |
| 13 | 95423851304600 |
| 14 | 1117539519314400 |
| 15 | 12986826568200000 |
| 16 | 149901793906152960 |
| 17 | 1720026938417810220 |
| 18 | 19632840460239283200 |
| 19 | 223048221338080399800 |
[0,2,24,720,10080,157500,2128896,28420392, 363242880,4552582320,55888690000,676114951512, 8074566549504,95423851304600,1117539519314400, 12986826568200000,149901793906152960, 1720026938417810220,19632840460239283200, 223048221338080399800] |