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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 121 |
| 6 | 726 |
| 7 | 5082 |
| 8 | 40656 |
| 9 | 365905 |
| 10 | 3659050 |
| 11 | 40249550 |
| 12 | 482994600 |
| 13 | 6278929801 |
| 14 | 87905017214 |
| 15 | 1318575258210 |
| 16 | 21097204131360 |
| 17 | 358652470233121 |
| 18 | 6455744464196178 |
| 19 | 122659144819727382 |
| 20 | 2453182896394547640 |
| 21 | 51516840824285500441 |
| 22 | 1133370498134281009702 |
[0,1,2,6,24,121,726,5082,40656,365905,3659050, 40249550,482994600,6278929801,87905017214, 1318575258210,21097204131360,358652470233121, 6455744464196178,122659144819727382, 2453182896394547640,51516840824285500441, 1133370498134281009702] |