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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 21 |
| 5 | 126 |
| 6 | 1394 |
| 7 | 16808 |
| 8 | 266305 |
| 9 | 4785157 |
| 10 | 100390882 |
| 11 | 2357947692 |
| 12 | 61978939050 |
| 13 | 1792160394038 |
| 14 | 56707753666594 |
| 15 | 1946196290656824 |
| 16 | 72061992352890881 |
| 17 | 2862423051509815794 |
| 18 | 121441386937936123331 |
| 19 | 5480386857784802185940 |
| 20 | 262145000003883417004506 |
[1,2,4,21,126,1394,16808,266305,4785157,100390882, 2357947692,61978939050,1792160394038, 56707753666594,1946196290656824,72061992352890881, 2862423051509815794,121441386937936123331, 5480386857784802185940,262145000003883417004506] |