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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 6 |
| 3 | 13 |
| 4 | 45 |
| 5 | 122 |
| 6 | 373 |
| 7 | 1073 |
| 8 | 3182 |
| 9 | 9293 |
| 10 | 27349 |
| 11 | 80178 |
| 12 | 235509 |
| 13 | 691097 |
| 14 | 2028998 |
| 15 | 5955501 |
| 16 | 17482685 |
| 17 | 51318186 |
| 18 | 150642613 |
| 19 | 442198913 |
| 20 | 1298048350 |
| 21 | 3810328141 |
| 22 | 11184967717 |
| 23 | 32832705122 |
| 24 | 96378199989 |
| 25 | 282911661033 |
| 26 | 830468071222 |
| 27 | 2437782776365 |
| 28 | 7155946454541 |
[1,1,6,13,45,122,373,1073,3182,9293,27349,80178, 235509,691097,2028998,5955501,17482685,51318186, 150642613,442198913,1298048350,3810328141, 11184967717,32832705122,96378199989,282911661033, 830468071222,2437782776365,7155946454541] |