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| n | a(n) |
|---|---|
| 1 | 8 |
| 2 | 30 |
| 3 | 126 |
| 4 | 518 |
| 5 | 2138 |
| 6 | 8818 |
| 7 | 36374 |
| 8 | 150038 |
| 9 | 618890 |
| 10 | 2552850 |
| 11 | 10530214 |
| 12 | 43435926 |
| 13 | 179168218 |
| 14 | 739048370 |
| 15 | 3048489846 |
| 16 | 12574671318 |
| 17 | 51869078378 |
| 18 | 213954005138 |
| 19 | 882535756294 |
| 20 | 3640358873558 |
| 21 | 15016063240250 |
| 22 | 61939540321970 |
[8,30,126,518,2138,8818,36374,150038,618890, 2552850,10530214,43435926,179168218,739048370, 3048489846,12574671318,51869078378,213954005138, 882535756294,3640358873558,15016063240250, 61939540321970] |