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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 42 |
| 4 | 752 |
| 5 | 19360 |
| 6 | 654912 |
| 7 | 27546736 |
| 8 | 1388207872 |
| 9 | 81621893376 |
| 10 | 5488951731200 |
| 11 | 415721105434624 |
| 12 | 35026876903256064 |
| 13 | 3250356630453317632 |
| 14 | 329437813126362185728 |
| 15 | 36214170617862339840000 |
| 16 | 4291812357982293898231808 |
| 17 | 545518054282041342531076096 |
| 18 | 74032137722410904128877494272 |
| 19 | 10684317262536125210489796296704 |
| 20 | 1634019721630446295055397683200000 |
[1,4,42,752,19360,654912,27546736,1388207872, 81621893376,5488951731200,415721105434624, 35026876903256064,3250356630453317632, 329437813126362185728,36214170617862339840000, 4291812357982293898231808, 545518054282041342531076096, 74032137722410904128877494272, 10684317262536125210489796296704, 1634019721630446295055397683200000] |