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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 30 |
| 4 | 396 |
| 5 | 8360 |
| 6 | 256470 |
| 7 | 10619952 |
| 8 | 564959528 |
| 9 | 37370475648 |
| 10 | 3001942868490 |
| 11 | 287388158562560 |
| 12 | 32278318416029532 |
| 13 | 4197544986996581376 |
| 14 | 625014083479647028622 |
| 15 | 105554855135062180485120 |
| 16 | 20053957030647088382195280 |
| 17 | 4255329207190209023134564352 |
[1,1,4,30,396,8360,256470,10619952,564959528, 37370475648,3001942868490,287388158562560, 32278318416029532,4197544986996581376, 625014083479647028622,105554855135062180485120, 20053957030647088382195280, 4255329207190209023134564352] |