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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 20 |
| 3 | 1640 |
| 4 | 901424 |
| 5 | 1333386848 |
| 6 | 9762556479680 |
| 7 | 552311189659544960 |
| 8 | 178664076508334107310336 |
| 9 | 177339376736100844376103875072 |
| 10 | 928195308949863753322027981355832320 |
| 11 | 37279296908672313898400994512625009709475840 |
[2,20,1640,901424,1333386848,9762556479680, 552311189659544960,178664076508334107310336, 177339376736100844376103875072, 928195308949863753322027981355832320, 37279296908672313898400994512625009709475840] |