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| n | a(n) |
|---|---|
| 1 | 6 |
| 2 | 72 |
| 3 | 558 |
| 4 | 3744 |
| 5 | 23070 |
| 6 | 135288 |
| 7 | 764862 |
| 8 | 4214784 |
| 9 | 22773798 |
| 10 | 121158840 |
| 11 | 636821526 |
| 12 | 3312601632 |
| 13 | 17087666310 |
| 14 | 87499403544 |
| 15 | 445295758230 |
| 16 | 2253803314176 |
| 17 | 11353558220742 |
| 18 | 56952225122616 |
| 19 | 284620991825574 |
| 20 | 1417625514526560 |
| 21 | 7039475232292062 |
| 22 | 34860099689171064 |
| 23 | 172198320473193822 |
[6,72,558,3744,23070,135288,764862,4214784, 22773798,121158840,636821526,3312601632, 17087666310,87499403544,445295758230, 2253803314176,11353558220742,56952225122616, 284620991825574,1417625514526560,7039475232292062, 34860099689171064,172198320473193822] |