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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 6 |
| 3 | 12 |
| 4 | 104 |
| 5 | 356 |
| 6 | 4134 |
| 7 | 14572 |
| 8 | 190652 |
| 9 | 9588156 |
| 10 | 35791472 |
| 11 | 1908889156 |
| 12 | 27487843256 |
| 13 | 104715393912 |
| 14 | 1529755308212 |
| 15 | 86607687722856 |
| 16 | 4969489243995032 |
| 17 | 19215358445940816 |
| 18 | 1117984489315857512 |
| 19 | 16865594581677305360 |
| 20 | 65588423375098872068 |
| 21 | 3874762242354582408912 |
[2,6,12,104,356,4134,14572,190652,9588156, 35791472,1908889156,27487843256,104715393912, 1529755308212,86607687722856,4969489243995032, 19215358445940816,1117984489315857512, 16865594581677305360,65588423375098872068, 3874762242354582408912] |