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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 50 |
| 3 | 220 |
| 4 | 1563 |
| 5 | 9193 |
| 6 | 57744 |
| 7 | 356786 |
| 8 | 2215533 |
| 9 | 13752047 |
| 10 | 85343361 |
| 11 | 529807380 |
| 12 | 3288466317 |
| 13 | 20413201710 |
| 14 | 126710229626 |
| 15 | 786538847475 |
| 16 | 4882316701191 |
| 17 | 30306289156276 |
| 18 | 188121896133891 |
| 19 | 1167739500871746 |
| 20 | 7248574819342407 |
[2,50,220,1563,9193,57744,356786,2215533,13752047, 85343361,529807380,3288466317,20413201710, 126710229626,786538847475,4882316701191, 30306289156276,188121896133891,1167739500871746, 7248574819342407] |