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| n | a(n) |
|---|---|
| 1 | 3 |
| 2 | 6 |
| 3 | 21 |
| 4 | 78 |
| 5 | 291 |
| 6 | 1086 |
| 7 | 4053 |
| 8 | 15126 |
| 9 | 56451 |
| 10 | 210678 |
| 11 | 786261 |
| 12 | 2934366 |
| 13 | 10951203 |
| 14 | 40870446 |
| 15 | 152530581 |
| 16 | 569251878 |
| 17 | 2124476931 |
| 18 | 7928655846 |
| 19 | 29590146453 |
| 20 | 110431929966 |
| 21 | 412137573411 |
| 22 | 1538118363678 |
| 23 | 5740335881301 |
| 24 | 21423225161526 |
| 25 | 79952564764803 |
| 26 | 298387033897686 |
[3,6,21,78,291,1086,4053,15126,56451,210678, 786261,2934366,10951203,40870446,152530581, 569251878,2124476931,7928655846,29590146453, 110431929966,412137573411,1538118363678, 5740335881301,21423225161526,79952564764803, 298387033897686] |