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| n | a(n) |
|---|---|
| 1 | 6 |
| 2 | 42 |
| 3 | 316 |
| 4 | 2336 |
| 5 | 17392 |
| 6 | 130548 |
| 7 | 1019188 |
| 8 | 7890336 |
| 9 | 61161968 |
| 10 | 475132844 |
| 11 | 3699945144 |
| 12 | 28879091744 |
| 13 | 225894152416 |
| 14 | 1770414640688 |
| 15 | 13899856847820 |
| 16 | 107593063689176 |
| 17 | 841538380150180 |
| 18 | 6603291331821456 |
| 19 | 51928633005911364 |
[6,42,316,2336,17392,130548,1019188,7890336, 61161968,475132844,3699945144,28879091744, 225894152416,1770414640688,13899856847820, 107593063689176,841538380150180,6603291331821456, 51928633005911364] |