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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 40 |
| 5 | 400 |
| 6 | 4656 |
| 7 | 62944 |
| 8 | 1046144 |
| 9 | 20274048 |
| 10 | 438238720 |
| 11 | 10529132416 |
| 12 | 280439144448 |
| 13 | 8185848206848 |
| 14 | 259202608222208 |
| 15 | 8855252721592320 |
| 16 | 324989707586830336 |
| 17 | 12748521382531956736 |
| 18 | 532098814401540587520 |
| 19 | 23547710868033300004864 |
| 20 | 1101540715832518509854720 |
| 21 | 54307901369414002580422656 |
| 22 | 2814303585179538846791237632 |
| 23 | 152935335939643406489642008576 |
| 24 | 8696644113583584719506275041280 |
| 25 | 516469893784923819203984490496000 |
[1,2,6,40,400,4656,62944,1046144,20274048, 438238720,10529132416,280439144448,8185848206848, 259202608222208,8855252721592320, 324989707586830336,12748521382531956736, 532098814401540587520,23547710868033300004864, 1101540715832518509854720, 54307901369414002580422656, 2814303585179538846791237632, 152935335939643406489642008576, 8696644113583584719506275041280, 516469893784923819203984490496000] |