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| n | a(n) |
|---|---|
| 2 | 4 |
| 3 | 16 |
| 4 | 80 |
| 5 | 768 |
| 6 | 9536 |
| 7 | 223232 |
| 8 | 6867200 |
| 9 | 393936896 |
| 10 | 29989282816 |
| 11 | 4225123221504 |
| 12 | 795427838939136 |
| 13 | 275571189819113472 |
| 14 | 128240735455510216704 |
| 15 | 109332361699222156738560 |
| 16 | 125729867860804073988096000 |
| 17 | 263919716304200619134696816640 |
| 18 | 749827702212803707621023160729600 |
| 19 | 3876699219598969046471294814225694720 |
[4,16,80,768,9536,223232,6867200,393936896, 29989282816,4225123221504,795427838939136, 275571189819113472,128240735455510216704, 109332361699222156738560, 125729867860804073988096000, 263919716304200619134696816640, 749827702212803707621023160729600, 3876699219598969046471294814225694720] |