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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 15 |
| 3 | 88 |
| 4 | 567 |
| 5 | 3876 |
| 6 | 27607 |
| 7 | 202653 |
| 8 | 1522365 |
| 9 | 11647038 |
| 10 | 90435804 |
| 11 | 710855544 |
| 12 | 5645365576 |
| 13 | 45228648078 |
| 14 | 365109237801 |
| 15 | 2966862631856 |
| 16 | 24248879149005 |
| 17 | 199213507774365 |
| 18 | 1644138419038500 |
| 19 | 13625326165675698 |
| 20 | 113336685917785332 |
| 21 | 945931091151789808 |
[1,3,15,88,567,3876,27607,202653,1522365,11647038, 90435804,710855544,5645365576,45228648078, 365109237801,2966862631856,24248879149005, 199213507774365,1644138419038500, 13625326165675698,113336685917785332, 945931091151789808] |