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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 4 |
| 3 | 16 |
| 4 | 68 |
| 5 | 296 |
| 6 | 1312 |
| 7 | 5888 |
| 8 | 26672 |
| 9 | 121696 |
| 10 | 558464 |
| 11 | 2574848 |
| 12 | 11917952 |
| 13 | 55345408 |
| 14 | 257741824 |
| 15 | 1203224576 |
| 16 | 5629027072 |
| 17 | 26383656448 |
| 18 | 123868321792 |
| 19 | 582414688256 |
| 20 | 2742116907008 |
| 21 | 12926036258816 |
| 22 | 60998951747584 |
[0,1,4,16,68,296,1312,5888,26672,121696,558464, 2574848,11917952,55345408,257741824,1203224576, 5629027072,26383656448,123868321792,582414688256, 2742116907008,12926036258816,60998951747584] |