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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 18 |
| 2 | 288 |
| 3 | 4800 |
| 4 | 86400 |
| 5 | 1693440 |
| 6 | 36126720 |
| 7 | 836075520 |
| 8 | 20901888000 |
| 9 | 562028544000 |
| 10 | 16186422067200 |
| 11 | 497364605337600 |
| 12 | 16247243774361600 |
| 13 | 562404592189440000 |
| 14 | 20567939371499520000 |
| 15 | 792551263781781504000 |
| 16 | 32098326183162150912000 |
| 17 | 1363234794367239585792000 |
[1,18,288,4800,86400,1693440,36126720,836075520, 20901888000,562028544000,16186422067200, 497364605337600,16247243774361600, 562404592189440000,20567939371499520000, 792551263781781504000,32098326183162150912000, 1363234794367239585792000] |