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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 8 |
| 3 | 71 |
| 4 | 744 |
| 5 | 9129 |
| 6 | 129072 |
| 7 | 2071215 |
| 8 | 37237680 |
| 9 | 741975345 |
| 10 | 16236211320 |
| 11 | 387182170935 |
| 12 | 9995788416600 |
| 13 | 277792140828825 |
| 14 | 8269430130712800 |
| 15 | 262542617405726175 |
| 16 | 8855805158351474400 |
| 17 | 316285840413064454625 |
| 18 | 11924219190760084593000 |
| 19 | 473245342972281190686375 |
| 20 | 19722890048636406588957000 |
[0,1,8,71,744,9129,129072,2071215,37237680, 741975345,16236211320,387182170935,9995788416600, 277792140828825,8269430130712800, 262542617405726175,8855805158351474400, 316285840413064454625,11924219190760084593000, 473245342972281190686375, 19722890048636406588957000] |