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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 20 |
| 2 | 3850 |
| 3 | 1078000 |
| 4 | 355066250 |
| 5 | 128107903000 |
| 6 | 49001272897500 |
| 7 | 19520507080800000 |
| 8 | 8012558140822125000 |
| 9 | 3365274419145292500000 |
| 10 | 1439327869068441602250000 |
| 11 | 624739666805574817770000000 |
[1,20,3850,1078000,355066250,128107903000, 49001272897500,19520507080800000, 8012558140822125000,3365274419145292500000, 1439327869068441602250000, 624739666805574817770000000] |