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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 12 |
| 4 | 128 |
| 5 | 1920 |
| 6 | 37104 |
| 7 | 877184 |
| 8 | 24520320 |
| 9 | 791112960 |
| 10 | 28932902400 |
| 11 | 1182789053952 |
| 12 | 53447706998784 |
| 13 | 2645389044480000 |
| 14 | 142326283714836480 |
| 15 | 8270318699325112320 |
| 16 | 516187815998727389184 |
| 17 | 34440412737701955502080 |
| 18 | 2446191865021002009477120 |
| 19 | 184278436717136012676956160 |
[1,2,12,128,1920,37104,877184,24520320,791112960, 28932902400,1182789053952,53447706998784, 2645389044480000,142326283714836480, 8270318699325112320,516187815998727389184, 34440412737701955502080,2446191865021002009477120, 184278436717136012676956160] |