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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 14 |
| 4 | 120 |
| 5 | 2002 |
| 6 | 31668 |
| 7 | 846260 |
| 8 | 19669408 |
| 9 | 725520510 |
| 10 | 22302380100 |
| 11 | 1050565700340 |
| 12 | 40208894434800 |
| 13 | 2306233390653636 |
| 14 | 105690931811261384 |
| 15 | 7147427113615588360 |
| 16 | 381647055369434628224 |
| 17 | 29733096067155146595510 |
| 18 | 1812925835184119075505540 |
| 19 | 159895014723794744296802900 |
| 20 | 10961834110187084182910698000 |
[1,2,14,120,2002,31668,846260,19669408,725520510, 22302380100,1050565700340,40208894434800, 2306233390653636,105690931811261384, 7147427113615588360,381647055369434628224, 29733096067155146595510,1812925835184119075505540, 159895014723794744296802900, 10961834110187084182910698000] |