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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 6 |
| 3 | 19 |
| 4 | 66 |
| 5 | 232 |
| 6 | 794 |
| 7 | 2574 |
| 8 | 7797 |
| 9 | 22058 |
| 10 | 58469 |
| 11 | 146027 |
| 12 | 345578 |
| 13 | 779240 |
| 14 | 1682359 |
| 15 | 3492869 |
| 16 | 6999952 |
| 17 | 13585959 |
| 18 | 25610002 |
| 19 | 47004982 |
| 20 | 84187248 |
| 21 | 147421139 |
| 22 | 252829908 |
| 23 | 425319569 |
| 24 | 702767285 |
| 25 | 1141951244 |
| 26 | 1826839569 |
| 27 | 2880058656 |
| 28 | 4478585700 |
[2,6,19,66,232,794,2574,7797,22058,58469,146027, 345578,779240,1682359,3492869,6999952,13585959, 25610002,47004982,84187248,147421139,252829908, 425319569,702767285,1141951244,1826839569, 2880058656,4478585700] |