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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 6 |
| 3 | 51 |
| 4 | 760 |
| 5 | 15545 |
| 6 | 428256 |
| 7 | 15043483 |
| 8 | 653049664 |
| 9 | 34204348305 |
| 10 | 2118834917200 |
| 11 | 152834879685851 |
| 12 | 12670536337934256 |
| 13 | 1194143629239156505 |
| 14 | 126753440317516749660 |
| 15 | 15031687739886065433375 |
| 16 | 1977667235694725269563136 |
| 17 | 286890421090357737699794209 |
| 18 | 45637300134026406622214264592 |
[1,1,6,51,760,15545,428256,15043483,653049664, 34204348305,2118834917200,152834879685851, 12670536337934256,1194143629239156505, 126753440317516749660,15031687739886065433375, 1977667235694725269563136, 286890421090357737699794209, 45637300134026406622214264592] |