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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 56 |
| 3 | 1856 |
| 4 | 103936 |
| 5 | 8893952 |
| 6 | 1080485888 |
| 7 | 176673603584 |
| 8 | 37417114009600 |
| 9 | 9963927777050624 |
| 10 | 3258468236083331072 |
| 11 | 1283800576046355447808 |
| 12 | 599766792781193235398656 |
| 13 | 327833344685493011492110336 |
| 14 | 207273007354010852132258840576 |
| 15 | 150092604050210703675500571656192 |
| 16 | 123411833893721992920958314267803648 |
| 17 | 114350314285874476606422143072852770816 |
| 18 | 118597403963878781240540181376561622024192 |
| 19 | 136853838009919098121511181384398866938331136 |
[1,4,56,1856,103936,8893952,1080485888, 176673603584,37417114009600,9963927777050624, 3258468236083331072,1283800576046355447808, 599766792781193235398656, 327833344685493011492110336, 207273007354010852132258840576, 150092604050210703675500571656192, 123411833893721992920958314267803648, 114350314285874476606422143072852770816, 118597403963878781240540181376561622024192, 136853838009919098121511181384398866938331136] |