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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 7 |
| 3 | 28 |
| 4 | 145 |
| 5 | 896 |
| 6 | 6328 |
| 7 | 50212 |
| 8 | 441489 |
| 9 | 4248370 |
| 10 | 44306306 |
| 11 | 496991848 |
| 12 | 5959111223 |
| 13 | 75977511442 |
| 14 | 1025441134747 |
| 15 | 14594189335496 |
| 16 | 218290221112929 |
| 17 | 3421314388169988 |
| 18 | 56043004143343843 |
| 19 | 957209642080023286 |
| 20 | 17011439135301438016 |
| 21 | 313980693855333453740 |
[1,2,7,28,145,896,6328,50212,441489,4248370, 44306306,496991848,5959111223,75977511442, 1025441134747,14594189335496,218290221112929, 3421314388169988,56043004143343843, 957209642080023286,17011439135301438016, 313980693855333453740] |