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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 19 |
| 3 | 97 |
| 4 | 505 |
| 5 | 2629 |
| 6 | 13609 |
| 7 | 69997 |
| 8 | 357985 |
| 9 | 1822309 |
| 10 | 9241849 |
| 11 | 46731997 |
| 12 | 235754065 |
| 13 | 1187152789 |
| 14 | 5969306089 |
| 15 | 29980723597 |
| 16 | 150440439745 |
| 17 | 754349584069 |
| 18 | 3780337658329 |
| 19 | 18936047636797 |
| 20 | 94817676351025 |
| 21 | 474638135996149 |
[1,4,19,97,505,2629,13609,69997,357985,1822309, 9241849,46731997,235754065,1187152789,5969306089, 29980723597,150440439745,754349584069, 3780337658329,18936047636797,94817676351025, 474638135996149] |