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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 12 |
| 4 | 38 |
| 5 | 147 |
| 6 | 542 |
| 7 | 2025 |
| 8 | 8040 |
| 9 | 31830 |
| 10 | 126026 |
| 11 | 512397 |
| 12 | 2091005 |
| 13 | 8534552 |
| 14 | 35263659 |
| 15 | 146386680 |
| 16 | 608204284 |
| 17 | 2542561872 |
| 18 | 10671803324 |
| 19 | 44849685497 |
| 20 | 189137805612 |
| 21 | 800087487080 |
| 22 | 3389342949285 |
| 23 | 14389283370260 |
| 24 | 61229743794326 |
| 25 | 260908050824695 |
| 26 | 1113484169340549 |
| 27 | 4760259426285405 |
[1,1,4,12,38,147,542,2025,8040,31830,126026, 512397,2091005,8534552,35263659,146386680, 608204284,2542561872,10671803324,44849685497, 189137805612,800087487080,3389342949285, 14389283370260,61229743794326,260908050824695, 1113484169340549,4760259426285405] |