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| n | a(n) |
|---|---|
| 0 | 4 |
| 1 | 8 |
| 2 | 24 |
| 3 | 80 |
| 4 | 272 |
| 5 | 928 |
| 6 | 3168 |
| 7 | 10816 |
| 8 | 36928 |
| 9 | 126080 |
| 10 | 430464 |
| 11 | 1469696 |
| 12 | 5017856 |
| 13 | 17132032 |
| 14 | 58492416 |
| 15 | 199705600 |
| 16 | 681837568 |
| 17 | 2327939072 |
| 18 | 7948081152 |
| 19 | 27136446464 |
| 20 | 92649623552 |
| 21 | 316325601280 |
| 22 | 1080003158016 |
| 23 | 3687361429504 |
| 24 | 12589439401984 |
| 25 | 42983034748928 |
[4,8,24,80,272,928,3168,10816,36928,126080,430464, 1469696,5017856,17132032,58492416,199705600, 681837568,2327939072,7948081152,27136446464, 92649623552,316325601280,1080003158016, 3687361429504,12589439401984,42983034748928] |