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| n | a(n) |
|---|---|
| 1 | 306 |
| 2 | 1126 |
| 3 | 3744 |
| 4 | 12544 |
| 5 | 41844 |
| 6 | 140716 |
| 7 | 471308 |
| 8 | 1580152 |
| 9 | 5294132 |
| 10 | 17749124 |
| 11 | 59488776 |
| 12 | 199400040 |
| 13 | 668327516 |
| 14 | 2240142740 |
| 15 | 7508500744 |
| 16 | 25167109004 |
| 17 | 84355063048 |
| 18 | 282742241052 |
| 19 | 947697217680 |
| 20 | 3176499039060 |
| 21 | 10647009866132 |
[306,1126,3744,12544,41844,140716,471308,1580152, 5294132,17749124,59488776,199400040,668327516, 2240142740,7508500744,25167109004,84355063048, 282742241052,947697217680,3176499039060, 10647009866132] |