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| n | a(n) |
|---|---|
| 1 | 6 |
| 2 | 69 |
| 3 | 273 |
| 4 | 1620 |
| 5 | 10459 |
| 6 | 56472 |
| 7 | 329520 |
| 8 | 1939754 |
| 9 | 11093629 |
| 10 | 64352261 |
| 11 | 373456149 |
| 12 | 2157426998 |
| 13 | 12495027985 |
| 14 | 72358519251 |
| 15 | 418731599880 |
| 16 | 2424245121120 |
| 17 | 14034463137812 |
| 18 | 81239767215253 |
| 19 | 470300385462933 |
| 20 | 2722552167523200 |
[6,69,273,1620,10459,56472,329520,1939754, 11093629,64352261,373456149,2157426998, 12495027985,72358519251,418731599880, 2424245121120,14034463137812,81239767215253, 470300385462933,2722552167523200] |