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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 12 |
| 3 | 78 |
| 4 | 648 |
| 5 | 6300 |
| 6 | 72000 |
| 7 | 939960 |
| 8 | 13749120 |
| 9 | 223035120 |
| 10 | 3969907200 |
| 11 | 76890733920 |
| 12 | 1609732776960 |
| 13 | 36214043785920 |
| 14 | 871131980759040 |
| 15 | 22310233170825600 |
| 16 | 606026217929932800 |
| 17 | 17401756135956192000 |
| 18 | 526641334386809241600 |
| 19 | 16753142420507766873600 |
[1,3,12,78,648,6300,72000,939960,13749120, 223035120,3969907200,76890733920,1609732776960, 36214043785920,871131980759040,22310233170825600, 606026217929932800,17401756135956192000, 526641334386809241600,16753142420507766873600] |