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| n | a(n) |
|---|---|
| 2 | 4 |
| 3 | 12 |
| 4 | 42 |
| 5 | 152 |
| 6 | 562 |
| 7 | 2108 |
| 8 | 7986 |
| 9 | 30476 |
| 10 | 116950 |
| 11 | 450756 |
| 12 | 1743470 |
| 13 | 6763152 |
| 14 | 26299104 |
| 15 | 102478208 |
| 16 | 400032822 |
| 17 | 1563985172 |
| 18 | 6122945694 |
| 19 | 23999991452 |
| 20 | 94173327894 |
| 21 | 369881810616 |
| 22 | 1454036828992 |
| 23 | 5720448937528 |
| 24 | 22521468585822 |
| 25 | 88725551176384 |
[4,12,42,152,562,2108,7986,30476,116950,450756, 1743470,6763152,26299104,102478208,400032822, 1563985172,6122945694,23999991452,94173327894, 369881810616,1454036828992,5720448937528, 22521468585822,88725551176384] |