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| n | a(n) |
|---|---|
| 1 | 6 |
| 2 | 24 |
| 3 | 117 |
| 4 | 456 |
| 5 | 1962 |
| 6 | 7660 |
| 7 | 31897 |
| 8 | 125240 |
| 9 | 514300 |
| 10 | 2027832 |
| 11 | 8266707 |
| 12 | 32688296 |
| 13 | 132665572 |
| 14 | 525661108 |
| 15 | 2127110678 |
| 16 | 8440975288 |
| 17 | 34086061208 |
| 18 | 135418512296 |
| 19 | 546011521445 |
| 20 | 2171164829984 |
| 21 | 8744100796746 |
| 22 | 34795052216800 |
| 23 | 140006637363629 |
[6,24,117,456,1962,7660,31897,125240,514300, 2027832,8266707,32688296,132665572,525661108, 2127110678,8440975288,34086061208,135418512296, 546011521445,2171164829984,8744100796746, 34795052216800,140006637363629] |