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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 7 |
| 3 | 28 |
| 4 | 119 |
| 5 | 524 |
| 6 | 2363 |
| 7 | 10844 |
| 8 | 50446 |
| 9 | 237280 |
| 10 | 1126437 |
| 11 | 5389916 |
| 12 | 25967972 |
| 13 | 125868952 |
| 14 | 613385075 |
| 15 | 3003586196 |
| 16 | 14771851093 |
| 17 | 72936101780 |
| 18 | 361419276386 |
| 19 | 1796837068400 |
| 20 | 8960207761500 |
[1,2,7,28,119,524,2363,10844,50446,237280,1126437, 5389916,25967972,125868952,613385075,3003586196, 14771851093,72936101780,361419276386, 1796837068400,8960207761500] |